{"id":2823,"date":"2024-11-01T21:30:35","date_gmt":"2024-11-01T13:30:35","guid":{"rendered":"http:\/\/viplao.com\/?p=2823"},"modified":"2024-11-01T21:30:38","modified_gmt":"2024-11-01T13:30:38","slug":"%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5","status":"publish","type":"post","link":"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/","title":{"rendered":"\u6570\u5b57\u5316\u8fd0\u8425\u57fa\u7840\u6280\u80fd \u2013 SQL \u6570\u636e\u5206\u6790\u5e38\u7528\u8bed\u53e5"},"content":{"rendered":"\n<p><strong>01 \u57fa\u7840\u67e5\u8be2<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/p4.itc.cn\/q_70\/images03\/20231025\/0efb0ca622bc47d687b9d1ff92924b46.jpeg\" alt=\"\"\/><\/figure>\n\n\n\n<p><strong>02 \u5b57\u7b26\u4e32\\\u6570\u5b57\\\u65e5\u671f\u65f6\u95f4<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/p2.itc.cn\/q_70\/images03\/20231025\/c0ba3a97ad0f4078bb6bd28ca2aa4fcf.jpeg\" alt=\"\"\/><\/figure>\n\n\n\n<p><strong>03 \u805a\u5408\u6570\u636e\u67e5\u8be2<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/p3.itc.cn\/q_70\/images03\/20231025\/3920429de6a741819574e32ec9a3b6f5.jpeg\" alt=\"\"\/><\/figure>\n\n\n\n<p><strong>04 \u5b50\u67e5\u8be2<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/p3.itc.cn\/q_70\/images03\/20231025\/816184a33d574c7db2aaead1d8e8e89a.jpeg\" alt=\"\"\/><\/figure>\n\n\n\n<p><strong>05 \u8054\u63a5\\\u7ec4\u5408\u67e5\u8be2<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/p9.itc.cn\/q_70\/images03\/20231025\/d859549dba0f41cd9e657254ca9505a9.jpeg\" alt=\"\"\/><\/figure>\n\n\n\n<p><strong>06 \u9ad8\u7ea7\u67e5\u8be2<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/p8.itc.cn\/q_70\/images03\/20231025\/3455357770654e988f9bd4097456f7e9.jpeg\" alt=\"\"\/><\/figure>\n\n\n\n<p><strong>07 \u66f4\u65b0\u6570\u636e<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/p3.itc.cn\/q_70\/images03\/20231025\/90b6e809e20344e891682180669e7c7a.jpeg\" alt=\"\"\/><\/figure>\n\n\n\n<p><\/p>\n\n\n\n<p>SQL\u51fd\u6570\u5927\u5168\uff0c\u5206\u7c7b\u6e05\u6670\uff0c\u7edd\u5bf9\u503c\u5f97\u6536\u85cf\uff0c\u60f3\u4e0d\u8d77\u6765\u7528\u4ec0\u4e48\u51fd\u6570\u770b\u5b83\u5c31\u6ca1\u9519\u4e86\uff01<\/p>\n\n\n\n<p>\u4e0d\u591a\u5e9f\u8bdd\uff0c\u76f4\u63a5\u4e0a\u5e72\u8d27\u3002<\/p>\n\n\n\n<p>1\u3001\u805a\u5408\u51fd\u6570<\/p>\n\n\n\n<p>2\u3001\u6570\u5b57\u51fd\u6570<\/p>\n\n\n\n<p>3\u3001\u5b57\u7b26\u4e32\u51fd\u6570<\/p>\n\n\n\n<p>4\u3001\u65e5\u671f\u51fd\u6570<\/p>\n\n\n\n<p>5\u3001\u8f6c\u6362\u51fd\u6570<\/p>\n\n\n\n<p>6\u3001\u7cfb\u7edf\u51fd\u6570<\/p>\n\n\n\n<p>7\u3001\u6761\u4ef6\u51fd\u6570<\/p>\n\n\n\n<p>8\u3001\u52a0\u5bc6\u51fd\u6570<\/p>\n\n\n\n<p>\u6839\u636e\u6211\u7684\u7406\u89e3\uff0cSQL\u51fd\u6570\u53ef\u4ee5\u5212\u5206\u6210\u4e0a\u8ff0\u76848\u4e2a\u7c7b\u522b\uff0c\u63a5\u4e0b\u6765\u5c06\u4e00\u4e00\u4e3a\u5927\u5bb6\u4ecb\u7ecd\u3002<\/p>\n\n\n\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_71 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">\u6587\u7ae0\u76ee\u5f55<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 eztoc-toggle-hide-by-default' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#%E4%B8%80%E3%80%81%E8%81%9A%E5%90%88%E5%87%BD%E6%95%B0\" title=\"\u4e00\u3001\u805a\u5408\u51fd\u6570\">\u4e00\u3001\u805a\u5408\u51fd\u6570<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#%E4%BA%8C%E3%80%81%E6%95%B0%E5%AD%97%E5%87%BD%E6%95%B0\" title=\"\u4e8c\u3001\u6570\u5b57\u51fd\u6570\">\u4e8c\u3001\u6570\u5b57\u51fd\u6570<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#%E4%B8%89%E3%80%81%E5%AD%97%E7%AC%A6%E4%B8%B2%E5%87%BD%E6%95%B0\" title=\"\u4e09\u3001\u5b57\u7b26\u4e32\u51fd\u6570\">\u4e09\u3001\u5b57\u7b26\u4e32\u51fd\u6570<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#%E5%9B%9B%E3%80%81%E6%97%A5%E6%9C%9F%E5%87%BD%E6%95%B0\" title=\"\u56db\u3001\u65e5\u671f\u51fd\u6570\">\u56db\u3001\u65e5\u671f\u51fd\u6570<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#1%E3%80%81%E8%8E%B7%E5%8F%96%E6%97%B6%E9%97%B4\" title=\"1\u3001\u83b7\u53d6\u65f6\u95f4\">1\u3001\u83b7\u53d6\u65f6\u95f4<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#2%E3%80%81%E5%A2%9E%E5%8A%A0%E3%80%81%E5%87%8F%E5%B0%91%E6%97%A5%E6%9C%9F\" title=\"2\u3001\u589e\u52a0\u3001\u51cf\u5c11\u65e5\u671f\">2\u3001\u589e\u52a0\u3001\u51cf\u5c11\u65e5\u671f<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#%E4%BA%94%E3%80%81%E8%BD%AC%E6%8D%A2%E5%87%BD%E6%95%B0\" title=\"\u4e94\u3001\u8f6c\u6362\u51fd\u6570\">\u4e94\u3001\u8f6c\u6362\u51fd\u6570<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#1%E3%80%81%E4%B8%8B%E5%88%97%E4%B8%A4%E4%B8%AA%E5%87%BD%E6%95%B0%E7%94%A8%E4%BA%8E%E5%B0%86%EF%BC%88%E4%BB%BB%E4%BD%95%E7%B1%BB%E5%9E%8B%E7%9A%84%EF%BC%89%E5%80%BC%E8%BD%AC%E6%8D%A2%E4%B8%BA%E6%8C%87%E5%AE%9A%E7%9A%84%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B%E3%80%82\" title=\"1\u3001\u4e0b\u5217\u4e24\u4e2a\u51fd\u6570\u7528\u4e8e\u5c06\uff08\u4efb\u4f55\u7c7b\u578b\u7684\uff09\u503c\u8f6c\u6362\u4e3a\u6307\u5b9a\u7684\u6570\u636e\u7c7b\u578b\u3002\">1\u3001\u4e0b\u5217\u4e24\u4e2a\u51fd\u6570\u7528\u4e8e\u5c06\uff08\u4efb\u4f55\u7c7b\u578b\u7684\uff09\u503c\u8f6c\u6362\u4e3a\u6307\u5b9a\u7684\u6570\u636e\u7c7b\u578b\u3002<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#2%E3%80%81%E6%97%A5%E6%9C%9F%E7%9B%B8%E5%85%B3%E7%9A%84%E8%BD%AC%E6%8D%A2%E5%87%BD%E6%95%B0\" title=\"2\u3001\u65e5\u671f\u76f8\u5173\u7684\u8f6c\u6362\u51fd\u6570\">2\u3001\u65e5\u671f\u76f8\u5173\u7684\u8f6c\u6362\u51fd\u6570<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#3%E3%80%81%E5%85%B6%E4%BB%96\" title=\"3\u3001\u5176\u4ed6\">3\u3001\u5176\u4ed6<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#%E5%85%AD%E3%80%81%E7%B3%BB%E7%BB%9F%E5%87%BD%E6%95%B0\" title=\"\u516d\u3001\u7cfb\u7edf\u51fd\u6570\">\u516d\u3001\u7cfb\u7edf\u51fd\u6570<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#%E4%B8%83%E3%80%81%E6%9D%A1%E4%BB%B6%E5%87%BD%E6%95%B0\" title=\"\u4e03\u3001\u6761\u4ef6\u51fd\u6570\">\u4e03\u3001\u6761\u4ef6\u51fd\u6570<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#1%E3%80%81CASE\" title=\"1\u3001CASE()\">1\u3001CASE()<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#2%E3%80%81IF\" title=\"2\u3001IF()\">2\u3001IF()<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/#%E5%85%AB%E3%80%81%E5%8A%A0%E5%AF%86%E5%87%BD%E6%95%B0\" title=\"\u516b\u3001\u52a0\u5bc6\u51fd\u6570\">\u516b\u3001\u52a0\u5bc6\u51fd\u6570<\/a><\/li><\/ul><\/nav><\/div>\n<h2 class=\"wp-block-heading\" id=\"h_606485782_0\"><span class=\"ez-toc-section\" id=\"%E4%B8%80%E3%80%81%E8%81%9A%E5%90%88%E5%87%BD%E6%95%B0\"><\/span>\u4e00\u3001\u805a\u5408\u51fd\u6570<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>AVG(col) \u8fd4\u56de\u6307\u5b9a\u5217\u4e2d\u6240\u6709\u7684\u5e73\u5747\u503c\u3002\u4ec5\u7528\u4e8e\u6570\u5b57\u5217\u5e76\u81ea\u52a8\u5ffd\u7565NULL\u503c\u3002<\/p>\n\n\n\n<p>COUNT(col) \u8fd4\u56de\u6307\u5b9a\u5217\u4e2d\u975eNULL\u503c\u7684\u6570\u91cf\u3002\u53ef\u7528\u4e8e\u6570\u5b57\u548c\u5b57\u7b26\u5217\u3002<\/p>\n\n\n\n<p>COUNT(*) \u8fd4\u56de\u8868\u4e2d\u7684\u884c\u6570(\u5305\u62ec\u6709NULL\u503c\u7684\u5217)\u3002<\/p>\n\n\n\n<p>MAX(col) \u8fd4\u56de\u6307\u5b9a\u5217\u4e2d\u7684\u6700\u5927\u503c\uff0c\u5ffd\u7565NULL\u503c\u3002\u53ef\u7528\u4e8e\u6570\u5b57\u3001\u5b57\u7b26\u548c\u65e5\u671f\u65f6\u95f4\u5217\u3002<\/p>\n\n\n\n<p>MIN(col) \u8fd4\u56de\u6307\u5b9a\u5217\u4e2d\u7684\u6700\u5c0f\u503c\uff0c\u5ffd\u7565NULL\u503c\u3002\u53ef\u7528\u4e8e\u6570\u5b57\u3001\u5b57\u7b26\u548c\u65e5\u671f\u65f6\u95f4\u5217\u3002<\/p>\n\n\n\n<p>SUM(col) \u8fd4\u56de\u6307\u5b9a\u5217\u4e2d\u6240\u6709\u7684\u603b\u548c\uff0c\u5ffd\u7565NULL\u503c\u3002\u4ec5\u7528\u4e8e\u6570\u5b57\u5217\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h_606485782_1\"><span class=\"ez-toc-section\" id=\"%E4%BA%8C%E3%80%81%E6%95%B0%E5%AD%97%E5%87%BD%E6%95%B0\"><\/span>\u4e8c\u3001\u6570\u5b57\u51fd\u6570<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>ACOS(float_expr) \u8fd4\u56de\u89d2(\u4ee5\u5f27\u5ea6\u8868\u793a)\uff0c\u5b83\u7684\u4f59\u5f26\u503c\u8fd1\u4f3c\u4e8e\u6307\u5b9a\u7684\u6d6e\u70b9\u8868\u8fbe\u5f0f\u3002<\/p>\n\n\n\n<p>ASIN(float_expr) \u8fd4\u56de\u89d2(\u4ee5\u5f27\u5ea6\u8868\u793a)\uff0c\u5b83\u7684\u6b63\u5f26\u503c\u8fd1\u4f3c\u4e8e\u6307\u5b9a\u7684\u6d6e\u70b9\u8868\u8fbe\u5f0f\u3002<\/p>\n\n\n\n<p>ATAN(float_expr) \u8fd4\u56de\u89d2(\u4ee5\u5f27\u5ea6\u8868\u793a)\uff0c\u5b83\u7684\u6b63\u5207\u503c\u8fd1\u4f3c\u4e8e\u6307\u5b9a\u7684\u6d6e\u70b9\u8868\u8fbe\u5f0f\u3002<\/p>\n\n\n\n<p>ATN2(float_expr1\uff0c float_expr2) \u8fd4\u56de\u89d2(\u4ee5\u5f27\u5ea6\u8868\u793a)\uff0c\u5b83\u7684\u6b63\u5207\u503c\u5728\u4e24\u4e2a\u8fd1\u4f3c\u7684\u6d6e\u70b9\u8868\u8fbe\u5f0f\u4e4b\u95f4\u3002<\/p>\n\n\n\n<p>COS(float_expr) \u8fd4\u56de\u4ee5\u6d6e\u70b9\u8868\u8fbe\u5f0f\u8868\u793a\u7684\u8fd1\u4f3c\u4e8e\u6307\u5b9a\u89d2\u5ea6(\u4ee5\u5f27\u5ea6\u8868\u793a)\u7684\u4f59\u5f26\u4e09\u89d2\u51fd\u6570\u7684\u503c\u3002<\/p>\n\n\n\n<p>COT(float_expr) \u8fd4\u56de\u4ee5\u6d6e\u70b9\u8868\u8fbe\u5f0f\u8868\u793a\u7684\u8fd1\u4f3c\u4e8e\u6307\u5b9a\u89d2\u5ea6(\u4ee5\u5f27\u5ea6\u8868\u793a)\u7684\u4f59\u5207\u4e09\u89d2\u51fd\u6570\u7684\u503c\u3002<\/p>\n\n\n\n<p>SIN(float_expr) \u8fd4\u56de\u4ee5\u6d6e\u70b9\u8868\u8fbe\u5f0f\u8868\u793a\u7684\u8fd1\u4f3c\u4e8e\u6307\u5b9a\u89d2\u5ea6(\u4ee5\u5f27\u5ea6\u8868\u793a)\u7684\u6b63\u5f26\u4e09\u89d2\u51fd\u6570\u7684\u503c\u3002<\/p>\n\n\n\n<p>TAN(float_expr) \u8fd4\u56de\u4ee5\u6d6e\u70b9\u8868\u8fbe\u5f0f\u8868\u793a\u7684\u8fd1\u4f3c\u4e8e\u6307\u5b9a\u89d2\u5ea6(\u4ee5\u5f27\u5ea6\u8868\u793a)\u7684\u6b63\u5207\u4e09\u89d2\u51fd\u6570\u7684\u503c\u3002<\/p>\n\n\n\n<p>ABS(num_expr) \u8fd4\u56de\u6570\u503c\u8868\u8fbe\u5f0f\u7684\u7edd\u5bf9\u503c\u3002<\/p>\n\n\n\n<p>CEILING(num_expr) \u8fd4\u56de\u5927\u4e8e\u6216\u7b49\u4e8e\u6570\u503c\u8868\u8fbe\u5f0f\u7684\u6700\u5c0f\u6574\u6570\u3002<\/p>\n\n\n\n<p>FLOOR(num_expr) \u8fd4\u56de\u5c0f\u4e8e\u6216\u7b49\u4e8e\u6570\u503c\u8868\u8fbe\u5f0f\u7684\u6700\u5927\u6574\u6570\u3002<\/p>\n\n\n\n<p>DEGREES(num_expr)\u8fd4\u56de\u6570\u503c\u8868\u8fbe\u5f0f\u8868\u793a\u7684\u5f27\u5ea6\u503c\u5bf9\u5e94\u7684\u5ea6\u503c\u3002<\/p>\n\n\n\n<p>RADIANS(num_expr) \u8fd4\u56de\u6570\u503c\u8868\u8fbe\u5f0f\u8868\u793a\u7684\u5ea6\u503c\u5bf9\u5e94\u7684\u5f27\u5ea6\u503c\u3002<\/p>\n\n\n\n<p>EXP(float_expr) \u6839\u636e\u6307\u5b9a\u7684\u8fd1\u4f3c\u6d6e\u70b9\u8868\u8fbe\u5f0f\uff0c\u8fd4\u56de\u6307\u6570\u503c\u3002<\/p>\n\n\n\n<p>LOG(float_expr) \u6839\u636e\u6307\u5b9a\u7684\u8fd1\u4f3c\u6d6e\u70b9\u8868\u8fbe\u5f0f\uff0c\u8fd4\u56de\u81ea\u7136\u5bf9\u6570\u503c\u3002<\/p>\n\n\n\n<p>LOG10(float_expr) \u6839\u636e\u6307\u5b9a\u7684\u8fd1\u4f3c\u6d6e\u70b9\u8868\u8fbe\u5f0f\uff0c\u8fd4\u56de\u4ee510\u4e3a\u5e95\u7684\u5bf9\u6570\u3002<\/p>\n\n\n\n<p>POWER(num_expr\uff0cy) \u8fd4\u56de\u5e42\u4e3ay\u7684\u6570\u503c\u8868\u8fbe\u5f0f\u7684\u503c\u3002<\/p>\n\n\n\n<p>SQRT(float_expr) \u8fd4\u56de\u6307\u5b9a\u7684\u8fd1\u4f3c\u6d6e\u70b9\u8868\u8fbe\u5f0f\u7684\u5e73\u65b9\u6839\u3002<\/p>\n\n\n\n<p>SQUARE(float_expr) \u8fd4\u56de\u6d6e\u70b9\u8868\u8fbe\u5f0f\u7684\u5e73\u65b9\u503c\u3002<\/p>\n\n\n\n<p>PI() \u8fd4\u56de\u5e38\u91cf\u503c3.141592653589793\u3002<\/p>\n\n\n\n<p>RAND([seed]) \u968f\u673a\u8fd4\u56de\u76840\u52301\u4e4b\u95f4\u7684\u8fd1\u4f3c\u6d6e\u70b9\u503c\uff0c\u53ef\u4ee5\u5bf9seed\u6307\u5b9a\u4e3a\u6574\u6570\u8868\u8fbe\u5f0f(\u53ef\u9009)\u3002<\/p>\n\n\n\n<p>ROUND(num_expr\uff0clength) \u5bf9\u6570\u503c\u8868\u8fbe\u5f0f\u622a\u53d6\u6307\u5b9a\u7684\u957f\u5ea6\uff0c\u8fd4\u56de\u56db\u820d\u4e94\u5165\u540e\u7684\u503c\u3002<\/p>\n\n\n\n<p>SIGN(num_expr) \u5bf9\u6b63\u6570\u6267\u884c+1\u64cd\u4f5c\uff0c\u5bf9\u8d1f\u6570\u548c\u96f6\u6267\u884c-1\u64cd\u4f5c\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h_606485782_2\"><span class=\"ez-toc-section\" id=\"%E4%B8%89%E3%80%81%E5%AD%97%E7%AC%A6%E4%B8%B2%E5%87%BD%E6%95%B0\"><\/span>\u4e09\u3001\u5b57\u7b26\u4e32\u51fd\u6570<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u4e3b\u8981\u7528\u4e8echar\u548cvarchar\u6570\u636e\u7c7b\u578b\u3002<\/p>\n\n\n\n<p>Expr1+expr2 \u8fd4\u56de\u4e24\u4e2a\u8868\u8fbe\u5f0f\u7684\u7ec4\u5408\u5f62\u5f0f\u7684\u5b57\u7b26\u4e32\u3002<\/p>\n\n\n\n<p>CONCAT(char_expr1, char_expr2, char_exprn) \u8fd4\u56de\u8fde\u63a5\u7684\u5b57\u7b26\u4e32\u3002<\/p>\n\n\n\n<p>ASCII(char_expr) char_expr\u53ef\u4ee5\u662f\u6587\u5b57\u5b57\u7b26\uff0c\u5b57\u7b26\u4e32\u8868\u8fbe\u5f0f\u6216\u5217\u3002\u5982\u679cchar_expr\u6709\u591a\u4e2a\u5b57\u7b26\uff0c\u5219\u8be5\u51fd\u6570\u8fd4\u56de\u5176\u6700\u5de6\u4fa7\u5b57\u7b26\u7684ASCII\u4ee3\u7801\u503c\u3002<\/p>\n\n\n\n<p>CHAR(int_expr) \u8fd4\u56de\u5230\u4e4b\u95f4\u7684\u6574\u6570\u8868\u8fbe\u5f0f\u7684ASC\u2161\u5b57\u7b26\u503c\u3002\u5982\u679c\u8f93\u5165\u7684\u503c\u4e0d\u5728\u6709\u6548\u8303\u56f4\u5185,\u5219\u8fd4\u56deNULL\u3002<\/p>\n\n\n\n<p>CHARINDEX(&#8216;pattern&#8217;,char_expr) \u8fd4\u56de\u5b57\u7b26\u8868\u8fbe\u5f0f\u4e2d\u6307\u5b9a\u6a21\u5f0f\u7684\u8d77\u59cb\u4f4d\u7f6e\u3002<\/p>\n\n\n\n<p>PATINDEX(&#8216;%pattern%&#8217;,expr) \u8fd4\u56de\u8868\u8fbe\u5f0f\u4e2d\u6a21\u5f0f\u7b2c\u4e00\u6b21\u51fa\u73b0\u7684\u8d77\u59cb\u4f4d\u7f6e\u3002\u8fd4\u56de\u8868\u793a\u4e0d\u5b58\u5728\u6a21\u5f0f\u5f62\u5f0f\u3002<\/p>\n\n\n\n<p>FIELD(char_expr, char_expr1, char_expr2, char_expr3,&#8230;) \u5728char_expr\u4e4b\u540e\u7684\u5b57\u7b26\u4e32\u4e2d\u5bfb\u627echar_expr\uff0c\u5e76\u8fd4\u56de\u51fa\u73b0\u7684\u7d22\u5f15\u4f4d\u7f6e\u3002<\/p>\n\n\n\n<p>DIFFERENCE(char_expr1,char_expr2) \u6839\u636e\u6bd4\u8f83\u4e24\u4e2a\u5b57\u7b26\u8868\u8fbe\u5f0f\u7684\u76f8\u4f3c\u5ea6,\u8fd4\u56de\u5230\u4e4b\u95f4\u7684\u503c\u3002\u8868\u793a\u5339\u914d\u5ea6\u6700\u4f73\u3002<\/p>\n\n\n\n<p>SOUNDEX(char_expr) \u8bc4\u4f30\u4e24\u4e2a\u5b57\u7b26\u4e32\u7684\u76f8\u4f3c\u5ea6\u540e\u5f97\u5230\u7684\u4f4d\u4ee3\u7801\u3002<\/p>\n\n\n\n<p>LEN(char_expr) \u8fd4\u56de\u5b57\u7b26\u8868\u8fbe\u5f0f\u7684\u957f\u5ea6\u3002<\/p>\n\n\n\n<p>LOWER(char_expr) \u5c06\u5b57\u7b26\u8868\u8fbe\u5f0f\u5168\u90e8\u8f6c\u6362\u4e3a\u5c0f\u5199\u3002<\/p>\n\n\n\n<p>UPPER(char_expr) \u5c06\u5b57\u7b26\u8868\u8fbe\u5f0f\u5168\u90e8\u8f6c\u6362\u4e3a\u5927\u5199\u3002<\/p>\n\n\n\n<p>LTRIM(char_expr) \u8fd4\u56de\u5220\u9664\u6389\u524d\u9762\u7a7a\u683c\u7684\u5b57\u7b26\u8868\u8fbe\u5f0f\u3002<\/p>\n\n\n\n<p>RTRIM(char_expr) \u8fd4\u56de\u5220\u9664\u6389\u5176\u540e\u7a7a\u683c\u7684\u5b57\u7b26\u8868\u8fbe\u5f0f\u3002<\/p>\n\n\n\n<p>TRIM(char_expr ) \u8fd4\u56de\u5220\u9664\u6389\u5f00\u5934\u548c\u7ed3\u5c3e\u7a7a\u683c\u7684\u5b57\u7b26\u8868\u8fbe\u5f0f\u3002<\/p>\n\n\n\n<p>SPACE(int_expr) \u8fd4\u56de\u5305\u542b\u6307\u5b9a\u7a7a\u683c\u6570\u7684\u5b57\u7b26\u4e32\u3002<\/p>\n\n\n\n<p>REPLICATE(input_string,count) \u8fd4\u56de\u91cd\u590d\u6307\u5b9a\u6b21\u6570\u7684\u5b57\u7b26\u8868\u8fbe\u5f0f\u4ea7\u751f\u7684\u5b57\u7b26\u4e32\u3002<\/p>\n\n\n\n<p>RIGHT(char_expr,int_expr) \u8fd4\u56de\u4ece\u5b57\u7b26\u8868\u8fbe\u5f0f\u6700\u53f3\u7aef\u8d77\u6839\u636e\u6307\u5b9a\u7684\u5b57\u7b26\u4e2a\u6570\u5f97\u5230\u7684\u5b57\u7b26\u3002<\/p>\n\n\n\n<p>STUFF(char_expr1,start,length,char_expr2) \u4f7f\u7528\u5b57\u7b26\u8868\u8fbe\u5f0f\u66ff\u6362\u5b57\u7b26\u8868\u8fbe\u5f0f\u7684\u4e00\u90e8\u5206\u5b57\u7b26,\u4ece\u6307\u5b9a\u7684\u4f4d\u7f6e\u5f00\u59cb\u66ff\u6362\u6307\u5b9a\u7684\u957f\u5ea6\u3002<\/p>\n\n\n\n<p>SUBSTRING(char_expr,start,length) \u8fd4\u56de\u4ece\u5b57\u7b26\u8868\u8fbe\u5f0f\u7684\u6307\u5b9a\u4f4d\u7f6e\u5f00\u59cb,\u622a\u53d6\u6307\u5b9a\u957f\u5ea6\u5f97\u5230\u7684\u5b57\u7b26\u96c6\u3002<\/p>\n\n\n\n<p>STR(float_expr[,length[,decimal]]) \u8fd4\u56de\u6d6e\u70b9\u8868\u8fbe\u5f0f\u7684\u5b57\u7b26\u4e32\u8868\u793a\u6cd5\u3002<\/p>\n\n\n\n<p>OCT(char_expr) \u8fd4\u56de\u516b\u8fdb\u5236\u53c2\u6570\u7684\u5b57\u7b26\u4e32\u8868\u793a\u3002<\/p>\n\n\n\n<p>REVERSE(char_expr) \u53cd\u8f6c\u5b57\u7b26\u8868\u8fbe\u5f0f\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h_606485782_3\"><span class=\"ez-toc-section\" id=\"%E5%9B%9B%E3%80%81%E6%97%A5%E6%9C%9F%E5%87%BD%E6%95%B0\"><\/span>\u56db\u3001\u65e5\u671f\u51fd\u6570<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h_606485782_4\"><span class=\"ez-toc-section\" id=\"1%E3%80%81%E8%8E%B7%E5%8F%96%E6%97%B6%E9%97%B4\"><\/span>1\u3001\u83b7\u53d6\u65f6\u95f4<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>GETDATE() \u5f53\u524d\u7684\u7cfb\u7edf\u65e5\u671f\u3002<\/p>\n\n\n\n<p>select GETDATE() &#8212; 2019-05-07 18:34:27.343<\/p>\n\n\n\n<p><em>#\u83b7\u53d6\u5f53\u524d\u65e5\u671f\u8fd8\u53ef\u4f7f\u7528CURRENT_TIMESTAMP()\u3001LOCALTIME()\u3001LOCALTIMESTAMP()\u3002<\/em><\/p>\n\n\n\n<p>DATENAME(\u65e5\u671f\u90e8\u5206,date) \u8fd4\u56de\u65e5\u671f\u4e2d\u65e5\u671f\u90e8\u5206\u7684\u5b57\u7b26\u4e32\u5f62\u5f0f\u3002<\/p>\n\n\n\n<p>select DATENAME(dw,GETDATE()) &#8212; \u661f\u671f\u4e8c<\/p>\n\n\n\n<p>\u6ce8\uff1aDATENAME \u548c DATEPART \u7684\u533a\u522b\uff0c\u8fd4\u56de\u7684\u503c\u7c7b\u578b\u4e0d\u540c\uff0c\u4e00\u4e2a\u662fVARCHAR\u4e00\u4e2a\u662fINT\uff0c\u53e6\u5916\u5c31\u662f\u661f\u671f\u4f1a\u7528\u672c\u5730\u8bed\u8a00\u6765\u8868\u793a<\/p>\n\n\n\n<p>DATEPART(\u65e5\u671f\u90e8\u5206,date) \u8fd4\u56de\u65e5\u671f\u4e2d\u6307\u5b9a\u7684\u65e5\u671f\u90e8\u5206\u7684\u6574\u6570\u5f62\u5f0f\u3002<\/p>\n\n\n\n<p>select DATEPART(dw,GETDATE()) &#8212; (\u8fd4\u56de\u4eca\u5929\u662f\u4e00\u5468\u4e2d\u7684\u7b2c\u51e0\u5929)\uff1a3<\/p>\n\n\n\n<p>YEAR(date) \u8fd4\u56de\u6307\u5b9a\u65e5\u671f\u7684\u5e74\u4efd\u6570\u503c<\/p>\n\n\n\n<p>select YEAR(GETDATE()) &#8212; 2019<\/p>\n\n\n\n<p>MONTH(date)\u8fd4\u56de\u6307\u5b9a\u65e5\u671f\u7684\u6708\u4efd\u6570\u503c<\/p>\n\n\n\n<p>DAY(date)\u8fd4\u56de\u6307\u5b9a\u65e5\u671f\u7684\u5929\u6570\u503c<\/p>\n\n\n\n<p>\u8fd8\u53ef\u4f7f\u7528EXTRACT()\u62bd\u53d6\u65e5\u671f\u3002<\/p>\n\n\n\n<p># \u5bf9\u4e8e\u65f6\u95f42021-04-02 09:25:29\uff0c\u5206\u522b\u83b7\u53d6\u5176\u5e74\u3001\u6708\u3001\u65e5\u3001\u65f6\u3001\u5206\u3001\u79d2<\/p>\n\n\n\n<p>SELECT EXTRACT(YEAR FROM NOW()); # 2021<\/p>\n\n\n\n<p>SELECT EXTRACT(MONTH FROM NOW()); # 4<\/p>\n\n\n\n<p>SELECT EXTRACT(DAY FROM NOW()); # 2<\/p>\n\n\n\n<p>SELECT EXTRACT(HOUR FROM NOW()); # 9<\/p>\n\n\n\n<p>SELECT EXTRACT(MINUTE FROM NOW()); # 25<\/p>\n\n\n\n<p>SELECT EXTRACT(SECOND FROM NOW()); # 29<\/p>\n\n\n\n<p># \u6216\u8005\u4ece\u65e5\u671f\u683c\u5f0f\u5b57\u7b26\u4e32\u4e2d\u83b7\u53d6<\/p>\n\n\n\n<p>SELECT EXTRACT(SECOND FROM &#8216;2021-04-02 10:37:14.123456&#8217;); # 14<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h_606485782_5\"><span class=\"ez-toc-section\" id=\"2%E3%80%81%E5%A2%9E%E5%8A%A0%E3%80%81%E5%87%8F%E5%B0%91%E6%97%A5%E6%9C%9F\"><\/span>2\u3001\u589e\u52a0\u3001\u51cf\u5c11\u65e5\u671f<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p># \u65f6\u95f4\u51cf\u5c111\u5c0f\u65f6\uff08\u524d\u4e00\u5c0f\u65f6\uff09<\/p>\n\n\n\n<p>select date_sub(now(), INTERVAL 1 hour);<\/p>\n\n\n\n<p># \u65e5\u671f\u589e\u52a01\u5929<\/p>\n\n\n\n<p>select date_add(now(), INTERVAL 1 day);<\/p>\n\n\n\n<p># \u5176\u4ed6\u95f4\u9694<\/p>\n\n\n\n<p>YEAR\u3001MONTH\u3001DAY\u3001HOUR\u3001MINUTE\u3001SECOND<\/p>\n\n\n\n<p>\u4ee5\u4e0b\u8f83\u5168\u7684MySQL\u65e5\u671f\u51fd\u6570\u52a0\u793a\u4f8b\u53ef\u505a\u53c2\u8003\uff08\u539f\u6587\u94fe\u63a5\uff1a<a href=\"https:\/\/link.zhihu.com\/?target=https%3A\/\/blog.csdn.net\/qinshijangshan\/article\/details\/72874667\" target=\"_blank\" rel=\"noreferrer noopener\">https:\/\/blog.csdn.net\/qinshijangshan\/article\/details\/72874667<\/a><\/p>\n\n\n\n<p>&#8212; MySQL\u65e5\u671f\u65f6\u95f4\u5904\u7406\u51fd\u6570<\/p>\n\n\n\n<p>&#8212; \u5f53\u524d\u65e5\u671f\uff1a2017-05-12\uff08\u7a81\u7136\u53d1\u73b0\u4eca\u5929512\uff0c\u662f\u4e0d\u662f\u4f1a\u62c9\u9632\u7a7a\u8b66\u62a5\uff09<\/p>\n\n\n\n<p>SELECT NOW() FROM DUAL;&#8211; \u5f53\u524d\u65e5\u671f\u65f6\u95f4\uff1a2017-05-12 11:41:47<\/p>\n\n\n\n<p>&#8212; \u5728MySQL\u91cc\u4e5f\u5b58\u5728\u548cOracle\u91cc\u7c7b\u4f3c\u7684dual\u865a\u62df\u8868\uff1a\u5b98\u65b9\u58f0\u660e\u7eaf\u7cb9\u662f\u4e3a\u4e86\u6ee1\u8db3select &#8230; from&#8230;\u8fd9\u4e00\u4e60\u60ef\u95ee\u9898\uff0cmysql\u4f1a\u5ffd\u7565\u5bf9\u8be5\u8868\u7684\u5f15\u7528\u3002<\/p>\n\n\n\n<p>&#8212; \u90a3\u4e48MySQL\u4e2d\u5c31\u4e0d\u7528DUAL\u4e86\u5427\u3002<\/p>\n\n\n\n<p>SELECT NOW();&#8211; \u5f53\u524d\u65e5\u671f\u65f6\u95f4\uff1a2017-05-12 11:41:55<\/p>\n\n\n\n<p>&#8212; \u9664\u4e86 now() \u51fd\u6570\u80fd\u83b7\u5f97\u5f53\u524d\u7684\u65e5\u671f\u65f6\u95f4\u5916\uff0cMySQL \u4e2d\u8fd8\u6709\u4e0b\u9762\u7684\u51fd\u6570\uff1a<\/p>\n\n\n\n<p>SELECT CURRENT_TIMESTAMP();&#8211; 2017-05-15 10:19:31<\/p>\n\n\n\n<p>SELECT CURRENT_TIMESTAMP;&#8211; 2017-05-15 10:19:51<\/p>\n\n\n\n<p>SELECT LOCALTIME();&#8211; 2017-05-15 10:20:00<\/p>\n\n\n\n<p>SELECT LOCALTIME;&#8211; 2017-05-15 10:20:10<\/p>\n\n\n\n<p>SELECT LOCALTIMESTAMP();&#8211; 2017-05-15 10:20:21(v4.0.6)<\/p>\n\n\n\n<p>SELECT LOCALTIMESTAMP;&#8211; 2017-05-15 10:20:30(v4.0.6)<\/p>\n\n\n\n<p>&#8212; \u8fd9\u4e9b\u65e5\u671f\u65f6\u95f4\u51fd\u6570\uff0c\u90fd\u7b49\u540c\u4e8e now()\u3002\u9274\u4e8e now() \u51fd\u6570\u7b80\u77ed\u6613\u8bb0\uff0c\u5efa\u8bae\u603b\u662f\u4f7f\u7528 now()\u6765\u66ff\u4ee3\u4e0a\u9762\u5217\u51fa\u7684\u51fd\u6570\u3002<\/p>\n\n\n\n<p>SELECT SYSDATE();&#8211; \u5f53\u524d\u65e5\u671f\u65f6\u95f4\uff1a2017-05-12 11:42:03<\/p>\n\n\n\n<p>&#8212; sysdate() \u65e5\u671f\u65f6\u95f4\u51fd\u6570\u8ddf now() \u7c7b\u4f3c\uff0c<\/p>\n\n\n\n<p>&#8212; \u4e0d\u540c\u4e4b\u5904\u5728\u4e8e\uff1anow() \u5728\u6267\u884c\u5f00\u59cb\u65f6\u503c\u5c31\u5f97\u5230\u4e86;sysdate() \u5728\u51fd\u6570\u6267\u884c\u65f6\u52a8\u6001\u5f97\u5230\u503c\u3002<\/p>\n\n\n\n<p>&#8212; \u770b\u4e0b\u9762\u7684\u4f8b\u5b50\u5c31\u660e\u767d\u4e86\uff1a<\/p>\n\n\n\n<p>SELECT NOW(), SLEEP(3), NOW();<\/p>\n\n\n\n<p>SELECT SYSDATE(), SLEEP(3), SYSDATE();<\/p>\n\n\n\n<p>SELECT CURDATE();&#8211; \u5f53\u524d\u65e5\u671f\uff1a2017-05-12<\/p>\n\n\n\n<p>SELECT CURRENT_DATE();&#8211; \u5f53\u524d\u65e5\u671f\uff1a\u7b49\u540c\u4e8e CURDATE()<\/p>\n\n\n\n<p>SELECT CURRENT_DATE;&#8211; \u5f53\u524d\u65e5\u671f\uff1a\u7b49\u540c\u4e8e CURDATE()<\/p>\n\n\n\n<p>SELECT CURTIME();&#8211; \u5f53\u524d\u65f6\u95f4\uff1a11:42:47<\/p>\n\n\n\n<p>SELECT CURRENT_TIME();&#8211; \u5f53\u524d\u65f6\u95f4\uff1a\u7b49\u540c\u4e8e CURTIME()<\/p>\n\n\n\n<p>SELECT CURRENT_TIME;&#8211; \u5f53\u524d\u65f6\u95f4\uff1a\u7b49\u540c\u4e8e CURTIME()<\/p>\n\n\n\n<p>&#8212; \u83b7\u5f97\u5f53\u524d UTC \u65e5\u671f\u65f6\u95f4\u51fd\u6570<\/p>\n\n\n\n<p>SELECT UTC_TIMESTAMP(), UTC_DATE(), UTC_TIME()<\/p>\n\n\n\n<p>&#8212; MySQL \u83b7\u5f97\u5f53\u524d\u65f6\u95f4\u6233\u51fd\u6570\uff1acurrent_timestamp, current_timestamp()<\/p>\n\n\n\n<p>SELECT CURRENT_TIMESTAMP, CURRENT_TIMESTAMP();&#8211; 2017-05-15 10:32:21 | 2017-05-15 10:32:21<\/p>\n\n\n\n<p>&#8212; MySQL \u65e5\u671f\u65f6\u95f4 Extract\uff08\u9009\u53d6\uff09 \u51fd\u6570<\/p>\n\n\n\n<p>SET @dt = &#8216;2017-05-15 10:37:14.123456&#8217;;<\/p>\n\n\n\n<p>SELECT DATE(@dt);&#8211; \u83b7\u53d6\u65e5\u671f\uff1a2017-05-15<\/p>\n\n\n\n<p>SELECT TIME(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; \u83b7\u53d6\u65f6\u95f4\uff1a10:37:14.123456<\/p>\n\n\n\n<p>SELECT YEAR(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; \u83b7\u53d6\u5e74\u4efd<\/p>\n\n\n\n<p>SELECT MONTH(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; \u83b7\u53d6\u6708\u4efd<\/p>\n\n\n\n<p>SELECT DAY(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; \u83b7\u53d6\u65e5<\/p>\n\n\n\n<p>SELECT HOUR(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; \u83b7\u53d6\u65f6<\/p>\n\n\n\n<p>SELECT MINUTE(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; \u83b7\u53d6\u5206<\/p>\n\n\n\n<p>SELECT SECOND(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; \u83b7\u53d6\u79d2<\/p>\n\n\n\n<p>SELECT MICROSECOND(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; \u83b7\u53d6\u6beb\u79d2<\/p>\n\n\n\n<p>SELECT QUARTER(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; \u83b7\u53d6\u5b63\u5ea6<\/p>\n\n\n\n<p>SELECT WEEK(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 20 (\u83b7\u53d6\u5468)<\/p>\n\n\n\n<p>SELECT WEEK(&#8216;2017-05-15 10:37:14.123456&#8217;, 7);&#8211; ****** \u6d4b\u8bd5\u6b64\u51fd\u6570\u5728MySQL5.6\u4e0b\u65e0\u6548<\/p>\n\n\n\n<p>SELECT WEEKOFYEAR(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; \u540cweek()<\/p>\n\n\n\n<p>SELECT DAYOFYEAR(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 135 (\u65e5\u671f\u5728\u5e74\u5ea6\u4e2d\u7b2c\u51e0\u5929)<\/p>\n\n\n\n<p>SELECT DAYOFMONTH(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 5 (\u65e5\u671f\u5728\u6708\u5ea6\u4e2d\u7b2c\u51e0\u5929)<\/p>\n\n\n\n<p>SELECT DAYOFWEEK(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 2 (\u65e5\u671f\u5728\u5468\u4e2d\u7b2c\u51e0\u5929\uff1b\u5468\u65e5\u4e3a\u7b2c\u4e00\u5929)<\/p>\n\n\n\n<p>SELECT WEEKDAY(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 0<\/p>\n\n\n\n<p>SELECT WEEKDAY(&#8216;2017-05-21 10:37:14.123456&#8217;);&#8211; 6(\u4e0edayofweek()\u90fd\u8868\u793a\u65e5\u671f\u5728\u5468\u7684\u7b2c\u51e0\u5929\uff0c\u53ea\u662f\u53c2\u8003\u6807\u51c6\u4e0d\u540c\uff0cweekday()\u5468\u4e00\u4e3a\u7b2c0\u5929\uff0c\u5468\u65e5\u4e3a\u7b2c6\u5929)<\/p>\n\n\n\n<p>SELECT YEARWEEK(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 201720(\u5e74\u548c\u5468)<\/p>\n\n\n\n<p>SELECT EXTRACT(YEAR FROM &#8216;2017-05-15 10:37:14.123456&#8217;);<\/p>\n\n\n\n<p>SELECT EXTRACT(MONTH FROM &#8216;2017-05-15 10:37:14.123456&#8217;);<\/p>\n\n\n\n<p>SELECT EXTRACT(DAY FROM &#8216;2017-05-15 10:37:14.123456&#8217;);<\/p>\n\n\n\n<p>SELECT EXTRACT(HOUR FROM &#8216;2017-05-15 10:37:14.123456&#8217;);<\/p>\n\n\n\n<p>SELECT EXTRACT(MINUTE FROM &#8216;2017-05-15 10:37:14.123456&#8217;);<\/p>\n\n\n\n<p>SELECT EXTRACT(SECOND FROM &#8216;2017-05-15 10:37:14.123456&#8217;);<\/p>\n\n\n\n<p>SELECT EXTRACT(MICROSECOND FROM &#8216;2017-05-15 10:37:14.123456&#8217;);<\/p>\n\n\n\n<p>SELECT EXTRACT(QUARTER FROM &#8216;2017-05-15 10:37:14.123456&#8217;);<\/p>\n\n\n\n<p>SELECT EXTRACT(WEEK FROM &#8216;2017-05-15 10:37:14.123456&#8217;);<\/p>\n\n\n\n<p>SELECT EXTRACT(YEAR_MONTH FROM &#8216;2017-05-15 10:37:14.123456&#8217;);<\/p>\n\n\n\n<p>SELECT EXTRACT(DAY_HOUR FROM &#8216;2017-05-15 10:37:14.123456&#8217;);<\/p>\n\n\n\n<p>SELECT EXTRACT(DAY_MINUTE FROM &#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 151037(\u65e5\u65f6\u5206)<\/p>\n\n\n\n<p>SELECT EXTRACT(DAY_SECOND FROM &#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 15103714(\u65e5\u65f6\u5206\u79d2)<\/p>\n\n\n\n<p>SELECT EXTRACT(DAY_MICROSECOND FROM &#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 15103714123456(\u65e5\u65f6\u5206\u79d2\u6beb\u79d2)<\/p>\n\n\n\n<p>SELECT EXTRACT(HOUR_MINUTE FROM &#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 1037(\u65f6\u5206)<\/p>\n\n\n\n<p>SELECT EXTRACT(HOUR_SECOND FROM &#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 103714(\u65f6\u5206\u79d2)<\/p>\n\n\n\n<p>SELECT EXTRACT(HOUR_MICROSECOND FROM &#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 103714123456(\u65e5\u65f6\u5206\u79d2\u6beb\u79d2)<\/p>\n\n\n\n<p>SELECT EXTRACT(MINUTE_SECOND FROM &#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 3714(\u5206\u79d2)<\/p>\n\n\n\n<p>SELECT EXTRACT(MINUTE_MICROSECOND FROM &#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 3714123456(\u5206\u79d2\u6beb\u79d2)<\/p>\n\n\n\n<p>SELECT EXTRACT(SECOND_MICROSECOND FROM &#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; 14123456(\u79d2\u6beb\u79d2)<\/p>\n\n\n\n<p>&#8212; MySQL Extract() \u51fd\u6570\u9664\u4e86\u6ca1\u6709date(),time() \u7684\u529f\u80fd\u5916\uff0c\u5176\u4ed6\u529f\u80fd\u4e00\u5e94\u5177\u5168\u3002<\/p>\n\n\n\n<p>&#8212; \u5e76\u4e14\u8fd8\u5177\u6709\u9009\u53d6\u2018day_microsecond&#8217; \u7b49\u529f\u80fd\u3002<\/p>\n\n\n\n<p>&#8212; \u6ce8\u610f\u8fd9\u91cc\u4e0d\u662f\u53ea\u9009\u53d6 day \u548c microsecond\uff0c\u800c\u662f\u4ece\u65e5\u671f\u7684 day \u90e8\u5206\u4e00\u76f4\u9009\u53d6\u5230 microsecond \u90e8\u5206\u3002<\/p>\n\n\n\n<p>SELECT DAYNAME(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; Monday(\u8fd4\u56de\u82f1\u6587\u661f\u671f)<\/p>\n\n\n\n<p>SELECT MONTHNAME(&#8216;2017-05-15 10:37:14.123456&#8217;);&#8211; May(\u8fd4\u56de\u82f1\u6587\u6708\u4efd)<\/p>\n\n\n\n<p>SELECT LAST_DAY(&#8216;2016-02-01&#8217;);&#8211; 2016-02-29 (\u8fd4\u56de\u6708\u4efd\u4e2d\u6700\u540e\u4e00\u5929)<\/p>\n\n\n\n<p>SELECT LAST_DAY(&#8216;2016-05-01&#8217;);&#8211; 2016-05-31<\/p>\n\n\n\n<p>&#8212; DATE_ADD(date,INTERVAL expr type) \u4ece\u65e5\u671f\u52a0\u4e0a\u6307\u5b9a\u7684\u65f6\u95f4\u95f4\u9694<\/p>\n\n\n\n<p>&#8212; type\u53c2\u6570\u53ef\u53c2\u8003\uff1a<a href=\"https:\/\/link.zhihu.com\/?target=http%3A\/\/www.w3school.com.cn\/sql\/func_date_sub.asp\" target=\"_blank\" rel=\"noreferrer noopener\">http:\/\/www.w3school.com.cn\/sql\/func_date_sub.asp<\/a><\/p>\n\n\n\n<p>SELECT DATE_ADD(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 YEAR);&#8211; \u8868\u793a\uff1a2018-05-15 10:37:14.123456<\/p>\n\n\n\n<p>SELECT DATE_ADD(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 QUARTER);&#8211; \u8868\u793a\uff1a2017-08-15 10:37:14.123456<\/p>\n\n\n\n<p>SELECT DATE_ADD(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 MONTH);&#8211; \u8868\u793a\uff1a2017-06-15 10:37:14.123456<\/p>\n\n\n\n<p>SELECT DATE_ADD(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 WEEK);&#8211; \u8868\u793a\uff1a2017-05-22 10:37:14.123456<\/p>\n\n\n\n<p>SELECT DATE_ADD(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 DAY);&#8211; \u8868\u793a\uff1a2017-05-16 10:37:14.123456<\/p>\n\n\n\n<p>SELECT DATE_ADD(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 HOUR);&#8211; \u8868\u793a\uff1a2017-05-15 11:37:14.123456<\/p>\n\n\n\n<p>SELECT DATE_ADD(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 MINUTE);&#8211; \u8868\u793a\uff1a2017-05-15 10:38:14.123456<\/p>\n\n\n\n<p>SELECT DATE_ADD(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 SECOND);&#8211; \u8868\u793a\uff1a2017-05-15 10:37:15.123456<\/p>\n\n\n\n<p>SELECT DATE_ADD(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 MICROSECOND);&#8211; \u8868\u793a\uff1a2017-05-15 10:37:14.123457<\/p>\n\n\n\n<p>&#8212; DATE_SUB(date,INTERVAL expr type) \u4ece\u65e5\u671f\u51cf\u53bb\u6307\u5b9a\u7684\u65f6\u95f4\u95f4\u9694<\/p>\n\n\n\n<p>SELECT DATE_SUB(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 YEAR);&#8211; \u8868\u793a\uff1a2016-05-15 10:37:14.123456<\/p>\n\n\n\n<p>SELECT DATE_SUB(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 QUARTER);&#8211; \u8868\u793a\uff1a2017-02-15 10:37:14.123456<\/p>\n\n\n\n<p>SELECT DATE_SUB(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 MONTH);&#8211; \u8868\u793a\uff1a2017-04-15 10:37:14.123456<\/p>\n\n\n\n<p>SELECT DATE_SUB(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 WEEK);&#8211; \u8868\u793a\uff1a2017-05-08 10:37:14.123456<\/p>\n\n\n\n<p>SELECT DATE_SUB(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 DAY);&#8211; \u8868\u793a\uff1a2017-05-14 10:37:14.123456<\/p>\n\n\n\n<p>SELECT DATE_SUB(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 HOUR);&#8211; \u8868\u793a\uff1a2017-05-15 09:37:14.123456<\/p>\n\n\n\n<p>SELECT DATE_SUB(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 MINUTE);&#8211; \u8868\u793a\uff1a2017-05-15 10:36:14.123456<\/p>\n\n\n\n<p>SELECT DATE_SUB(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 SECOND);&#8211; \u8868\u793a\uff1a2017-05-15 10:37:13.123456<\/p>\n\n\n\n<p>SELECT DATE_SUB(&#8216;2017-05-15 10:37:14.123456&#8217;,INTERVAL 1 MICROSECOND);&#8211; \u8868\u793a\uff1a2017-05-15 10:37:14.123455<\/p>\n\n\n\n<p>&#8212; \u7ecf\u7279\u6b8a\u65e5\u671f\u6d4b\u8bd5\uff0cDATE_SUB(date,INTERVAL expr type)\u53ef\u653e\u5fc3\u4f7f\u7528<\/p>\n\n\n\n<p>SELECT DATE_SUB(CURDATE(),INTERVAL 1 DAY);&#8211; \u524d\u4e00\u5929\uff1a2017-05-11<\/p>\n\n\n\n<p>SELECT DATE_SUB(CURDATE(),INTERVAL -1 DAY);&#8211; \u540e\u4e00\u5929\uff1a2017-05-13<\/p>\n\n\n\n<p>SELECT DATE_SUB(CURDATE(),INTERVAL 1 MONTH);&#8211; \u4e00\u4e2a\u6708\u524d\u65e5\u671f\uff1a2017-04-12<\/p>\n\n\n\n<p>SELECT DATE_SUB(CURDATE(),INTERVAL -1 MONTH);&#8211; \u4e00\u4e2a\u6708\u540e\u65e5\u671f\uff1a2017-06-12<\/p>\n\n\n\n<p>SELECT DATE_SUB(CURDATE(),INTERVAL 1 YEAR);&#8211; \u4e00\u5e74\u524d\u65e5\u671f\uff1a2016-05-12<\/p>\n\n\n\n<p>SELECT DATE_SUB(CURDATE(),INTERVAL -1 YEAR);&#8211; \u4e00\u5e74\u540e\u65e5\u671f\uff1a20178-06-12<\/p>\n\n\n\n<p>&#8212; MySQL date_sub() \u65e5\u671f\u65f6\u95f4\u51fd\u6570 \u548c date_add() \u7528\u6cd5\u4e00\u81f4\uff0c\u5e76\u4e14\u53ef\u4ee5\u7528INTERNAL -1 xxx\u7684\u5f62\u5f0f\u4e92\u6362\u4f7f\u7528\uff1b<\/p>\n\n\n\n<p>&#8212; \u53e6\u5916\uff0cMySQL \u4e2d\u8fd8\u6709\u4e24\u4e2a\u51fd\u6570 subdate(), subtime()\uff0c\u5efa\u8bae\uff0c\u7528 date_sub() \u6765\u66ff\u4ee3\u3002<\/p>\n\n\n\n<p>&#8212; MySQL \u53e6\u7c7b\u65e5\u671f\u51fd\u6570\uff1aperiod_add(P,N), period_diff(P1,P2)<\/p>\n\n\n\n<p>&#8212; \u51fd\u6570\u53c2\u6570\u201cP\u201d \u7684\u683c\u5f0f\u4e3a\u201cYYYYMM\u201d \u6216\u8005 \u201cYYMM\u201d\uff0c\u7b2c\u4e8c\u4e2a\u53c2\u6570\u201cN\u201d \u8868\u793a\u589e\u52a0\u6216\u51cf\u53bb N month\uff08\u6708\uff09\u3002<\/p>\n\n\n\n<p>&#8212; MySQL period_add(P,N)\uff1a\u65e5\u671f\u52a0\/\u51cf\u53bbN\u6708\u3002<\/p>\n\n\n\n<p>SELECT PERIOD_ADD(201705,2), PERIOD_ADD(201705,-2);&#8211; 201707 20170503<\/p>\n\n\n\n<p>&#8212; period_diff(P1,P2)\uff1a\u65e5\u671f P1-P2\uff0c\u8fd4\u56de N \u4e2a\u6708\u3002<\/p>\n\n\n\n<p>SELECT PERIOD_DIFF(201706, 201703);&#8211;<\/p>\n\n\n\n<p>&#8212; datediff(date1,date2)\uff1a\u4e24\u4e2a\u65e5\u671f\u76f8\u51cf date1 &#8211; date2\uff0c\u8fd4\u56de\u5929\u6570<\/p>\n\n\n\n<p>SELECT DATEDIFF(&#8216;2017-06-05&#8242;,&#8217;2017-05-29&#8217;);&#8211; 7<\/p>\n\n\n\n<p>&#8212; TIMEDIFF(time1,time2)\uff1a\u4e24\u4e2a\u65e5\u671f\u76f8\u51cf time1 &#8211; time2\uff0c\u8fd4\u56de TIME \u5dee\u503c<\/p>\n\n\n\n<p>SELECT TIMEDIFF(&#8216;2017-06-05 19:28:37&#8217;, &#8216;2017-06-05 17:00:00&#8217;);&#8211; 02:28:37<\/p>\n\n\n\n<p>&#8212; MySQL\u65e5\u671f\u8f6c\u6362\u51fd\u6570<\/p>\n\n\n\n<p>SELECT TIME_TO_SEC(&#8217;01:00:05&#8242;); &#8212; 3605<\/p>\n\n\n\n<p>SELECT SEC_TO_TIME(3605);&#8211; 01:00:05<\/p>\n\n\n\n<p>&#8212; MySQL \uff08\u65e5\u671f\u3001\u5929\u6570\uff09\u8f6c\u6362\u51fd\u6570\uff1ato_days(date), from_days(days)<\/p>\n\n\n\n<p>SELECT TO_DAYS(&#8216;0000-00-00&#8217;); &#8212; NULL<\/p>\n\n\n\n<p>SELECT TO_DAYS(&#8216;2017-06-05&#8217;); &#8212; 736850<\/p>\n\n\n\n<p>SELECT FROM_DAYS(0); &#8212; &#8216;0000-00-00&#8217;<\/p>\n\n\n\n<p>SELECT FROM_DAYS(736850); &#8212; &#8216;2017-06-05&#8217;<\/p>\n\n\n\n<p>&#8212; MySQL Str to Date \uff08\u5b57\u7b26\u4e32\u8f6c\u6362\u4e3a\u65e5\u671f\uff09\u51fd\u6570\uff1astr_to_date(str, format)<\/p>\n\n\n\n<p>SELECT STR_TO_DATE(&#8216;06.05.2017 19:40:30&#8217;, &#8216;%m.%d.%Y %H:%i:%s&#8217;);&#8211; 2017-06-05 19:40:30<\/p>\n\n\n\n<p>SELECT STR_TO_DATE(&#8217;06\/05\/2017&#8242;, &#8216;%m\/%d\/%Y&#8217;); &#8212; 2017-06-05<\/p>\n\n\n\n<p>SELECT STR_TO_DATE(&#8216;2017\/12\/3&#8242;,&#8217;%Y\/%m\/%d&#8217;) &#8212; 2017-12-03<\/p>\n\n\n\n<p>SELECT STR_TO_DATE(&#8217;20:09:30&#8242;, &#8216;%h:%i:%s&#8217;) &#8212; NULL(\u8d85\u8fc712\u65f6\u7684\u5c0f\u65f6\u7528\u5c0f\u5199h\uff0c\u5f97\u5230\u7684\u7ed3\u679c\u4e3aNULL)<\/p>\n\n\n\n<p>&#8212; \u65e5\u671f\u65f6\u95f4\u683c\u5f0f\u5316<\/p>\n\n\n\n<p>SELECT DATE_FORMAT(&#8216;2017-05-12 17:03:51&#8217;, &#8216;%Y\u5e74%m\u6708%d\u65e5 %H\u65f6%i\u5206%s\u79d2&#8217;);&#8211; 2017\u5e7405\u670812\u65e5 17\u65f603\u520651\u79d2(\u5177\u4f53\u9700\u8981\u4ec0\u4e48\u683c\u5f0f\u7684\u6570\u636e\u6839\u636e\u5b9e\u9645\u60c5\u51b5\u6765;\u5c0f\u5199h\u4e3a12\u5c0f\u65f6\u5236;)<\/p>\n\n\n\n<p>SELECT TIME_FORMAT(&#8216;2017-05-12 17:03:51&#8217;, &#8216;%Y\u5e74%m\u6708%d\u65e5 %H\u65f6%i\u5206%s\u79d2&#8217;);&#8211; 0000\u5e7400\u670800\u65e5 17\u65f603\u520651\u79d2(time_format()\u53ea\u80fd\u7528\u4e8e\u65f6\u95f4\u7684\u683c\u5f0f\u5316)<\/p>\n\n\n\n<p>&#8212; STR_TO_DATE()\u548cDATE_FORMATE()\u4e3a\u4e92\u9006\u64cd\u4f5c<\/p>\n\n\n\n<p>&#8212; MySQL \u83b7\u5f97\u56fd\u5bb6\u5730\u533a\u65f6\u95f4\u683c\u5f0f\u51fd\u6570\uff1aget_format()<\/p>\n\n\n\n<p>&#8212; MySQL get_format() \u8bed\u6cd5\uff1aget_format(date|time|datetime, &#8216;eur&#8217;|&#8217;usa&#8217;|&#8217;jis&#8217;|&#8217;iso&#8217;|&#8217;internal&#8217;<\/p>\n\n\n\n<p>&#8212; MySQL get_format() \u7528\u6cd5\u7684\u5168\u90e8\u793a\u4f8b\uff1a<\/p>\n\n\n\n<p>SELECT GET_FORMAT(DATE,&#8217;usa&#8217;); &#8212; &#8216;%m.%d.%Y&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(DATE,&#8217;jis&#8217;); &#8212; &#8216;%Y-%m-%d&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(DATE,&#8217;iso&#8217;); &#8212; &#8216;%Y-%m-%d&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(DATE,&#8217;eur&#8217;); &#8212; &#8216;%d.%m.%Y&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(DATE,&#8217;internal&#8217;); &#8212; &#8216;%Y%m%d&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(DATETIME,&#8217;usa&#8217;); &#8212; &#8216;%Y-%m-%d %H.%i.%s&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(DATETIME,&#8217;jis&#8217;); &#8212; &#8216;%Y-%m-%d %H:%i:%s&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(DATETIME,&#8217;iso&#8217;); &#8212; &#8216;%Y-%m-%d %H:%i:%s&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(DATETIME,&#8217;eur&#8217;); &#8212; &#8216;%Y-%m-%d %H.%i.%s&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(DATETIME,&#8217;internal&#8217;); &#8212; &#8216;%Y%m%d%H%i%s&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(TIME,&#8217;usa&#8217;); &#8212; &#8216;%h:%i:%s %p&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(TIME,&#8217;jis&#8217;); &#8212; &#8216;%H:%i:%s&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(TIME,&#8217;iso&#8217;); &#8212; &#8216;%H:%i:%s&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(TIME,&#8217;eur&#8217;); &#8212; &#8216;%H.%i.%s&#8217;<\/p>\n\n\n\n<p>SELECT GET_FORMAT(TIME,&#8217;internal&#8217;); &#8212; &#8216;%H%i%s&#8217;<\/p>\n\n\n\n<p>&#8212; MySQL \u62fc\u51d1\u65e5\u671f\u3001\u65f6\u95f4\u51fd\u6570\uff1amakdedate(year,dayofyear), maketime(hour,minute,second)<\/p>\n\n\n\n<p>SELECT MAKEDATE(2017,31); &#8212; &#8216;2017-01-31&#8217;<\/p>\n\n\n\n<p>SELECT MAKEDATE(2017,32); &#8212; &#8216;2017-02-01&#8217;<\/p>\n\n\n\n<p>SELECT MAKETIME(19,52,35); &#8212; &#8217;19:52:35&#8242;<\/p>\n\n\n\n<p>&#8212; MySQL \u65f6\u533a\uff08timezone\uff09\u8f6c\u6362\u51fd\u6570\uff1aconvert_tz(dt,from_tz,to_tz)<\/p>\n\n\n\n<p>SELECT CONVERT_TZ(&#8216;2017-06-05 19:54:12&#8217;, &#8216;+08:00&#8217;, &#8216;+00:00&#8217;); &#8212; 2017-06-05 11:54:12<\/p>\n\n\n\n<p>&#8212; MySQL \uff08Unix \u65f6\u95f4\u6233\u3001\u65e5\u671f\uff09\u8f6c\u6362\u51fd\u6570<\/p>\n\n\n\n<p>&#8212; unix_timestamp(), unix_timestamp(date), from_unixtime(unix_timestamp), from_unixtime(unix_timestamp,format)<\/p>\n\n\n\n<p>&#8212; \u5c06\u5177\u4f53\u65f6\u95f4\u65f6\u95f4\u8f6c\u4e3atimestamp<\/p>\n\n\n\n<p>SELECT UNIX_TIMESTAMP();&#8211; \u5f53\u524d\u65f6\u95f4\u7684\u65f6\u95f4\u6233\uff1a1494815779<\/p>\n\n\n\n<p>SELECT UNIX_TIMESTAMP(&#8216;2017-05-15&#8217;);&#8211; \u6307\u5b9a\u65e5\u671f\u7684\u65f6\u95f4\u6233\uff1a1494777600<\/p>\n\n\n\n<p>SELECT UNIX_TIMESTAMP(&#8216;2017-05-15 10:37:14&#8217;);&#8211; \u6307\u5b9a\u65e5\u671f\u65f6\u95f4\u7684\u65f6\u95f4\u6233\uff1a1494815834<\/p>\n\n\n\n<p>&#8212; \u5c06\u65f6\u95f4\u6233\u8f6c\u4e3a\u5177\u4f53\u65f6\u95f4<\/p>\n\n\n\n<p>SELECT FROM_UNIXTIME(1494815834);&#8211; 2017-05-15 10:37:14<\/p>\n\n\n\n<p>SELECT FROM_UNIXTIME(1494815834, &#8216;%Y\u5e74%m\u6708%d\u65e5 %h\u65f6%\u5206:%s\u79d2&#8217;);&#8211; \u83b7\u53d6\u65f6\u95f4\u6233\u5bf9\u5e94\u7684\u683c\u5f0f\u5316\u65e5\u671f\u65f6\u95f4<\/p>\n\n\n\n<p>&#8212; MySQL \u65f6\u95f4\u6233\uff08timestamp\uff09\u8f6c\u6362\u3001\u589e\u3001\u51cf\u51fd\u6570<\/p>\n\n\n\n<p>SELECT TIMESTAMP(&#8216;2017-05-15&#8217;);&#8211; 2017-05-15 00:00:00<\/p>\n\n\n\n<p>SELECT TIMESTAMP(&#8216;2017-05-15 08:12:25&#8242;, &#8217;01:01:01&#8217;);&#8211; 2017-05-15 09:13:26<\/p>\n\n\n\n<p>SELECT DATE_ADD(&#8216;2017-05-15 08:12:25&#8217;, INTERVAL 1 DAY);&#8211; 2017-05-16 08:12:25<\/p>\n\n\n\n<p>SELECT TIMESTAMPADD(DAY, 1, &#8216;2017-05-15 08:12:25&#8217;);&#8211; 2017-05-16 08:12:25; MySQL timestampadd() \u51fd\u6570\u7c7b\u4f3c\u4e8e date_add()\u3002<\/p>\n\n\n\n<p>SELECT TIMESTAMPDIFF(YEAR, &#8216;2017-06-01&#8217;, &#8216;2016-05-15&#8217;);&#8211; -1<\/p>\n\n\n\n<p>SELECT TIMESTAMPDIFF(MONTH, &#8216;2017-06-01&#8217;, &#8216;2016-06-15&#8217;);&#8211; -11<\/p>\n\n\n\n<p>SELECT TIMESTAMPDIFF(DAY, &#8216;2017-06-01&#8217;, &#8216;2016-06-15&#8217;);&#8211; -351<\/p>\n\n\n\n<p>SELECT TIMESTAMPDIFF(HOUR, &#8216;2017-06-01 08:12:25&#8217;, &#8216;2016-06-15 00:00:00&#8217;);&#8211; -8432<\/p>\n\n\n\n<p>SELECT TIMESTAMPDIFF(MINUTE, &#8216;2017-06-01 08:12:25&#8217;, &#8216;2016-06-15 00:00:00&#8217;);&#8211; -505932<\/p>\n\n\n\n<p>SELECT TIMESTAMPDIFF(SECOND, &#8216;2017-06-01 08:12:25&#8217;, &#8216;2016-06-15 00:00:00&#8217;);&#8211; -30355945<\/p>\n\n\n\n<p><strong>SQL\u4e2d\u65e5\u671f\u7684\u8868\u793a\u65b9\u6cd5\u53ca\u6709\u6548\u8303\u56f4,\u5982\u4e0b:<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><td>\u65e5\u671f\u90e8\u5206<\/td><td>\u7f29\u5199<\/td><td>\u503c<\/td><td>\u65e5\u671f\u90e8\u5206<\/td><td>\u7f29\u5199<\/td><td>\u503c<\/td><\/tr><tr><td>\u5e74<\/td><td>yy<\/td><td>1753-9999<\/td><td>\u5468<\/td><td>wk<\/td><td>1-53<\/td><\/tr><tr><td>\u5b63\u5ea6<\/td><td>qq<\/td><td>1-4<\/td><td>\u5c0f\u65f6<\/td><td>hh<\/td><td>0-23<\/td><\/tr><tr><td>\u6708<\/td><td>mm<\/td><td>1-12<\/td><td>\u5206\u949f<\/td><td>mi<\/td><td>0-59<\/td><\/tr><tr><td>\u4e00\u5e74\u4e2d\u7684\u5929<\/td><td>dy<\/td><td>1-366<\/td><td>\u79d2<\/td><td>ss<\/td><td>0-59<\/td><\/tr><tr><td>\u4e00\u6708\u4e2d\u7684\u5929<\/td><td>dd<\/td><td>1-31<\/td><td>\u6beb\u79d2<\/td><td>ms<\/td><td>0-999<\/td><\/tr><tr><td>\u4e00\u5468\u4e2d\u7684\u5929<\/td><td>dw<\/td><td>1-7<\/td><td><\/td><td><\/td><td><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h_606485782_6\"><span class=\"ez-toc-section\" id=\"%E4%BA%94%E3%80%81%E8%BD%AC%E6%8D%A2%E5%87%BD%E6%95%B0\"><\/span>\u4e94\u3001\u8f6c\u6362\u51fd\u6570<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h_606485782_7\"><span class=\"ez-toc-section\" id=\"1%E3%80%81%E4%B8%8B%E5%88%97%E4%B8%A4%E4%B8%AA%E5%87%BD%E6%95%B0%E7%94%A8%E4%BA%8E%E5%B0%86%EF%BC%88%E4%BB%BB%E4%BD%95%E7%B1%BB%E5%9E%8B%E7%9A%84%EF%BC%89%E5%80%BC%E8%BD%AC%E6%8D%A2%E4%B8%BA%E6%8C%87%E5%AE%9A%E7%9A%84%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B%E3%80%82\"><\/span>1\u3001\u4e0b\u5217\u4e24\u4e2a\u51fd\u6570\u7528\u4e8e\u5c06\uff08\u4efb\u4f55\u7c7b\u578b\u7684\uff09\u503c\u8f6c\u6362\u4e3a\u6307\u5b9a\u7684\u6570\u636e\u7c7b\u578b\u3002<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>CONVERT(data_type[(length)], expression [, style])<\/p>\n\n\n\n<p><em>expression &#8211; \u8981\u8f6c\u6362\u7684\u8868\u8fbe\u5f0f\u3002<\/em><\/p>\n\n\n\n<p><em>datatype &#8211; \u8981\u5c06\u8868\u8fbe\u5f0f\u8f6c\u6362\u4e3a\u7684\u6570\u636e\u7c7b\u578b\u3002<\/em><\/p>\n\n\n\n<p><em>format &#8211; \u53ef\u9009-\u6307\u5b9a\u65e5\u671f\u548c\u65f6\u95f4\u683c\u5f0f\u7684\u6574\u6570\u4ee3\u7801\uff0c\u7528\u4e8e\u5728\u65e5\u671f\/\u65f6\u95f4\/\u65f6\u95f4\u6233\u6570\u636e\u7c7b\u578b\u548c\u5b57\u7b26\u6570\u636e\u7c7b\u578b\u4e4b\u95f4\u8fdb\u884c\u8f6c\u6362\u3002<\/em><\/p>\n\n\n\n<p>CAST(expression AS datatype(length))<\/p>\n\n\n\n<p><em>expression &#8211; \u8981\u8f6c\u6362\u7684\u8868\u8fbe\u5f0f\u3002<\/em><\/p>\n\n\n\n<p><em>datatype &#8211; \u8981\u5c06\u8868\u8fbe\u5f0f\u8f6c\u6362\u4e3a\u7684\u6570\u636e\u7c7b\u578b\u3002<\/em><\/p>\n\n\n\n<p><em>length &#8211; \u53ef\u9009\u3002\u7ed3\u679c\u6570\u636e\u7c7b\u578b\u7684\u957f\u5ea6\uff08\u5bf9\u4e8e char\u3001varchar\u3001nchar\u3001nvarchar\u3001binary \u548c varbinary\uff09<\/em><\/p>\n\n\n\n<p>CAST \u548c CONVERT \u63d0\u4f9b\u76f8\u4f3c\u7684\u529f\u80fd\uff0c\u4f46\u8bed\u6cd5\u4e0d\u540c\u3002\u5728\u65f6\u95f4\u8f6c\u5316\u4e2d\u4e00\u822c\u7528convert,\u56e0\u4e3a\u5b83\u6bd4cast\u591a\u4e86\u4e00\u4e2astyle\uff0c\u53ef\u4ee5\u6839\u636e\u9700\u8981\u8f6c\u5316\u6210\u4e0d\u540c\u7684\u65f6\u95f4\u683c\u5f0f\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h_606485782_8\"><span class=\"ez-toc-section\" id=\"2%E3%80%81%E6%97%A5%E6%9C%9F%E7%9B%B8%E5%85%B3%E7%9A%84%E8%BD%AC%E6%8D%A2%E5%87%BD%E6%95%B0\"><\/span>2\u3001\u65e5\u671f\u76f8\u5173\u7684\u8f6c\u6362\u51fd\u6570<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p># \u8f6c\u6362\u65e5\u671f\u683c\u5f0f\uff1a<\/p>\n\n\n\n<p>DATE_FORMAT(date, format)<\/p>\n\n\n\n<p>select DATE_FORMAT(now(),&#8217;%Y-%m-%d %H:%i:%s&#8217;);<\/p>\n\n\n\n<p>select DATE_FORMAT(now(),&#8217;%Y-%m-%d %H:00:00&#8242;);<\/p>\n\n\n\n<p>#\u5b57\u7b26\u4e32\u8f6c\u65e5\u671f\u683c\u5f0f<\/p>\n\n\n\n<p>str_to_date(date, format)<\/p>\n\n\n\n<p>select str_to_date(&#8216;2021-04-02 10:37:14&#8217;, &#8216;%Y-%m-%d %H:%i:%s&#8217;); # 2021-04-02 10:37:14<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h_606485782_9\"><span class=\"ez-toc-section\" id=\"3%E3%80%81%E5%85%B6%E4%BB%96\"><\/span>3\u3001\u5176\u4ed6<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>FORMAT(column_name,format) \u7528\u4e8e\u5bf9\u5b57\u6bb5\u7684\u663e\u793a\u8fdb\u884c\u683c\u5f0f\u5316\u3002<\/p>\n\n\n\n<p>INET_ATON(ip) \u8fd4\u56deIP\u5730\u5740\u7684\u6570\u5b57\u8868\u793a\u3002<\/p>\n\n\n\n<p>INET_NTOA(num) \u8fd4\u56de\u6570\u5b57\u6240\u4ee3\u8868\u7684IP\u5730\u5740\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h_606485782_10\"><span class=\"ez-toc-section\" id=\"%E5%85%AD%E3%80%81%E7%B3%BB%E7%BB%9F%E5%87%BD%E6%95%B0\"><\/span>\u516d\u3001\u7cfb\u7edf\u51fd\u6570<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u7528\u4e8e\u8fd4\u56de\u5143\u6570\u636e\u6216\u76f8\u5173\u914d\u7f6e\u8bbe\u7f6e\u3002<\/p>\n\n\n\n<p>COALESCE(expr1,expr2, xprN) \u8fd4\u56de\u7b2c\u4e00\u4e2a\u975eNULL\u8868\u8fbe\u5f0f\u3002<\/p>\n\n\n\n<p>COL_LENGTH(&#8216;table_name&#8217;,&#8217;column_name&#8217;) \u8fd4\u56de\u5217\u7684\u957f\u5ea6\u3002<\/p>\n\n\n\n<p>COL_NAME(table_id,column_id) \u8fd4\u56de\u6307\u5b9a\u7684\u8868\u4e2d\u7684\u5217\u540d\u3002<\/p>\n\n\n\n<p>DATALENGTH(&#8216;expr&#8217;) \u8fd4\u56de\u4efb\u4f55\u6570\u636e\u7c7b\u578b\u7684\u5b9e\u9645\u957f\u5ea6\u3002<\/p>\n\n\n\n<p>DB_ID([\u2018database_name&#8217;]) \u8fd4\u56de\u6570\u636e\u5e93\u7684\u6807\u8bc6\u53f7\u3002<\/p>\n\n\n\n<p>DB_NAME([database_id]) \u8fd4\u56de\u6570\u636e\u5e93\u7684\u540d\u79f0\u3002<\/p>\n\n\n\n<p>GETANSINULL([\u2018database_name&#8217;]) \u8fd4\u56de\u6570\u636e\u5e93\u7684\u9ed8\u8ba4\u7a7a\u6027(Nullability)\u3002<\/p>\n\n\n\n<p>HOST_ID() \u8fd4\u56de\u5de5\u4f5c\u7ad9\u7684\u6807\u8bc6\u53f7\u3002<\/p>\n\n\n\n<p>HOST_NAME() \u8fd4\u56de\u5de5\u4f5c\u7ad9\u7684\u540d\u79f0\u3002<\/p>\n\n\n\n<p>IDENT_INCR(&#8216;table_or_view&#8217;) \u6709\u65b0\u7684\u8bb0\u5f55\u6dfb\u52a0\u5165\u5230\u8868\u4e2d\u65f6\u8ba1\u6570\u52a0\u3002<\/p>\n\n\n\n<p>IDENT_SEED(&#8216;table_or_view&#8217;) \u8fd4\u56de\u6807\u8bc6\u5217\u7684\u8d77\u59cb\u7f16\u53f7\u3002<\/p>\n\n\n\n<p>INDEX_COL(&#8216;table_name&#8217;,index_id,key_id) \u8fd4\u56de\u7d22\u5f15\u7684\u5217\u540d\u3002<\/p>\n\n\n\n<p>ISNULL(expr,value) \u4f7f\u7528\u6307\u5b9a\u7684\u503c\u66ff\u6362\u7684NULL\u8868\u8fbe\u5f0f\u3002<\/p>\n\n\n\n<p>NULLIF(expr1,expr2) Expr1\u4e0eExpr2\u76f8\u7b49\u65f6,\u8fd4\u56deNull\u3002<\/p>\n\n\n\n<p>OBJECT_ID(&#8216;obj_name&#8217;) \u8fd4\u56de\u6570\u636e\u5e93\u5bf9\u8c61\u6807\u8bc6\u53f7\u3002<\/p>\n\n\n\n<p>OBJECT_NAME(&#8216;object_id&#8217;) \u8fd4\u56de\u6570\u636e\u5e93\u5bf9\u8c61\u540d\u3002<\/p>\n\n\n\n<p>STATS_DATE(table_id,index_id) \u8fd4\u56de\u4e0a\u6b21\u66f4\u65b0\u6307\u5b9a\u7d22\u5f15\u7684\u7edf\u8ba1\u7684\u65e5\u671f\u3002<\/p>\n\n\n\n<p>SUSER_SID([\u2018login_name&#8217;]) \u8fd4\u56de\u7528\u6237\u7684\u767b\u5f55\u6807\u8bc6\u53f7\u3002<\/p>\n\n\n\n<p>SUSER_ID([\u2018login_name&#8217;]) \u8fd4\u56de\u7528\u6237\u7684\u767b\u5f55\u6807\u8bc6\u53f7\u3002\u8fd9\u4e2a\u51fd\u6570\u7c7b\u4f3c\u4e8eSUSER_SID()\u51fd\u6570,\u5e76\u4e14\u4fdd\u7559\u4e86\u5411\u540e\u7684\u517c\u5bb9\u6027\u3002<\/p>\n\n\n\n<p>SUSER_SNAME([server_user_id]) \u8fd4\u56de\u7528\u6237\u7684\u767b\u5f55\u6807\u8bc6\u53f7\u3002<\/p>\n\n\n\n<p>SUSER_NAME([server_user_id]) \u8fd4\u56de\u7528\u6237\u7684\u767b\u5f55\u6807\u8bc6\u53f7\u3002\u8fd9\u4e2a\u51fd\u6570\u7c7b\u4f3c\u4e8eSUSER_SNAME()\u51fd\u6570,\u5e76\u4e14\u4fdd\u7559\u4e86\u5411\u540e\u7684\u517c\u5bb9\u6027\u3002<\/p>\n\n\n\n<p>USER_ID(&#8216;user_name&#8217;) \u8fd4\u56de\u7528\u6237\u7684\u6570\u636e\u5e93\u6807\u8bc6\u53f7\u3002<\/p>\n\n\n\n<p>USER_NAME([&#8216;user_id&#8217;]) \u8fd4\u56de\u7528\u6237\u7684\u6570\u636e\u5e93\u540d\u79f0\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h_606485782_11\"><span class=\"ez-toc-section\" id=\"%E4%B8%83%E3%80%81%E6%9D%A1%E4%BB%B6%E5%87%BD%E6%95%B0\"><\/span>\u4e03\u3001\u6761\u4ef6\u51fd\u6570<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u6761\u4ef6\u51fd\u6570\u6709\u4e24\u7c7b\uff0c\u4e00\u7c7b\u662fCASE()\uff0c\u53e6\u4e00\u7c7b\u662fIF()\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h_606485782_12\"><span class=\"ez-toc-section\" id=\"1%E3%80%81CASE\"><\/span>1\u3001CASE()<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>case()\u51fd\u6570\u6709\u4e24\u79cd\u5f62\u5f0f\uff0c\u5206\u4e3a\u7b80\u5355\u578b\u548c\u641c\u7d22\u578b<\/p>\n\n\n\n<p><strong>\u7b80\u5355\u641c\u7d22\uff1a<\/strong><\/p>\n\n\n\n<p>CASE V0<\/p>\n\n\n\n<p>WHEN V1 THEN E1<\/p>\n\n\n\n<p>WHEN V2 THEN E2<\/p>\n\n\n\n<p>WHEN VN THEN EN<\/p>\n\n\n\n<p>ELSE ED<\/p>\n\n\n\n<p>END;<\/p>\n\n\n\n<p><strong>\u590d\u6742\u641c\u7d22\uff1a<\/strong><\/p>\n\n\n\n<p>CASE<\/p>\n\n\n\n<p>WHEN condition1 THEN result1<\/p>\n\n\n\n<p>WHEN condition2 THEN result2<\/p>\n\n\n\n<p>WHEN conditionN THEN resultN<\/p>\n\n\n\n<p>ELSE result<\/p>\n\n\n\n<p>END;<\/p>\n\n\n\n<p>\u7b80\u5355\u7684case\u8868\u8fbe\u5f0f\u6ca1\u6709\u641c\u7d22\u578bcase\u8868\u8fbe\u5f0f\u7075\u6d3b\uff0c\u56e0\u4e3a\u65e0\u6cd5\u6307\u5b9a\u81ea\u5df1\u7684\u6761\u4ef6\uff0c\u800c\u641c\u7d22\u578bcase\u8868\u8fbe\u5f0f\u53ef\u4ee5\u5305\u542b\u8303\u56f4\u6761\u4ef6\u3001\u4e0d\u7b49\u6761\u4ef6\u3001\u4f7f\u7528and\/or\/not\u7ec4\u5408\u591a\u4e2a\u6761\u4ef6\uff0c\u6240\u4ee5\uff0c\u9664\u6700\u7b80\u5355\u7684\u903b\u8f91\u4e4b\u5916\uff0c\u4e00\u822c\u63a8\u8350\u4f7f\u7528\u641c\u7d22\u578bcase\u8868\u8fbe\u5f0f\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h_606485782_13\"><span class=\"ez-toc-section\" id=\"2%E3%80%81IF\"><\/span>2\u3001IF()<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>IF(condition, value_if_true, value_if_false)<\/p>\n\n\n\n<p>condition &#8212; \u8981\u8fdb\u884c\u5224\u65ad\u7684\u503c<\/p>\n\n\n\n<p>value_if_true &#8212; condition\u4e3a\u771f\u65f6\u8fd4\u56de\u7684\u503c<\/p>\n\n\n\n<p>value_if_false &#8212; condition\u4e3a\u5047\u65f6\u8fd4\u56de\u7684\u503c<\/p>\n\n\n\n<p>IF()\u51fd\u6570\u8fd8\u884d\u751f\u51fa\u4e86IFNULL()\u3001NULLIF()\u51fd\u6570\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h_606485782_14\"><span class=\"ez-toc-section\" id=\"%E5%85%AB%E3%80%81%E5%8A%A0%E5%AF%86%E5%87%BD%E6%95%B0\"><\/span>\u516b\u3001\u52a0\u5bc6\u51fd\u6570<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>AES_ENCRYPT(str,key) \u8fd4\u56de\u7528\u5bc6\u94a5key\u5bf9\u5b57\u7b26\u4e32str\u5229\u7528\u9ad8\u7ea7\u52a0\u5bc6\u6807\u51c6\u7b97\u6cd5\u52a0\u5bc6\u540e\u7684\u7ed3\u679c\uff0c\u8c03\u7528AES_ENCRYPT\u7684\u7ed3\u679c\u662f\u4e00\u4e2a\u4e8c\u8fdb\u5236\u5b57\u7b26\u4e32\uff0c\u4ee5BLOB\u7c7b\u578b\u5b58\u50a8<\/p>\n\n\n\n<p>AES_DECRYPT(str,key) \u8fd4\u56de\u7528\u5bc6\u94a5key\u5bf9\u5b57\u7b26\u4e32str\u5229\u7528\u9ad8\u7ea7\u52a0\u5bc6\u6807\u51c6\u7b97\u6cd5\u89e3\u5bc6\u540e\u7684\u7ed3\u679c<\/p>\n\n\n\n<p>DECODE(str,key) \u4f7f\u7528key\u4f5c\u4e3a\u5bc6\u94a5\u89e3\u5bc6\u52a0\u5bc6\u5b57\u7b26\u4e32str<\/p>\n\n\n\n<p>ENCRYPT(str,salt) \u4f7f\u7528UNIXcrypt()\u51fd\u6570\uff0c\u7528\u5173\u952e\u8bcdsalt(\u4e00\u4e2a\u53ef\u4ee5\u60df\u4e00\u786e\u5b9a\u53e3\u4ee4\u7684\u5b57\u7b26\u4e32\uff0c\u5c31\u50cf\u94a5\u5319\u4e00\u6837)\u52a0\u5bc6\u5b57\u7b26\u4e32str<\/p>\n\n\n\n<p>ENCODE(str,key) \u4f7f\u7528key\u4f5c\u4e3a\u5bc6\u94a5\u52a0\u5bc6\u5b57\u7b26\u4e32str\uff0c\u8c03\u7528ENCODE()\u7684\u7ed3\u679c\u662f\u4e00\u4e2a\u4e8c\u8fdb\u5236\u5b57\u7b26\u4e32\uff0c\u5b83\u4ee5BLOB\u7c7b\u578b\u5b58\u50a8<\/p>\n\n\n\n<p>MD5() \u8ba1\u7b97\u5b57\u7b26\u4e32str\u7684MD5\u6821\u9a8c\u548c<\/p>\n\n\n\n<p>PASSWORD(str) \u8fd4\u56de\u5b57\u7b26\u4e32str\u7684\u52a0\u5bc6\u7248\u672c\uff0c\u8fd9\u4e2a\u52a0\u5bc6\u8fc7\u7a0b\u662f\u4e0d\u53ef\u9006\u8f6c\u7684\uff0c\u548cUNIX\u5bc6\u7801\u52a0\u5bc6\u8fc7\u7a0b\u4f7f\u7528\u4e0d\u540c\u7684\u7b97\u6cd5\u3002<\/p>\n\n\n\n<p>SHA() \u8ba1\u7b97\u5b57\u7b26\u4e32str\u7684\u5b89\u5168\u6563\u5217\u7b97\u6cd5(SHA)\u6821\u9a8c\u548c<\/p>\n","protected":false},"excerpt":{"rendered":"<p>01 \u57fa\u7840\u67e5\u8be2 02 \u5b57\u7b26\u4e32\\\u6570\u5b57\\\u65e5\u671f\u65f6\u95f4 03 \u805a\u5408\u6570\u636e\u67e5\u8be2 04 \u5b50\u67e5\u8be2 05 \u8054\u63a5\\\u7ec4\u5408\u67e5\u8be2&hellip; <a href=\"http:\/\/viplao.com\/index.php\/2024\/11\/01\/%e6%95%b0%e5%ad%97%e5%8c%96%e8%bf%90%e8%90%a5%e5%9f%ba%e7%a1%80%e6%8a%80%e8%83%bd-sql-%e6%95%b0%e6%8d%ae%e5%88%86%e6%9e%90%e5%b8%b8%e7%94%a8%e8%af%ad%e5%8f%a5\/\" class=\"more-link read-more\" rel=\"bookmark\">\u7ee7\u7eed\u9605\u8bfb <span class=\"screen-reader-text\">\u6570\u5b57\u5316\u8fd0\u8425\u57fa\u7840\u6280\u80fd \u2013 SQL \u6570\u636e\u5206\u6790\u5e38\u7528\u8bed\u53e5<\/span><i class=\"fa fa-arrow-right\"><\/i><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[26],"views":1037,"_links":{"self":[{"href":"http:\/\/viplao.com\/index.php\/wp-json\/wp\/v2\/posts\/2823"}],"collection":[{"href":"http:\/\/viplao.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/viplao.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/viplao.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/viplao.com\/index.php\/wp-json\/wp\/v2\/comments?post=2823"}],"version-history":[{"count":2,"href":"http:\/\/viplao.com\/index.php\/wp-json\/wp\/v2\/posts\/2823\/revisions"}],"predecessor-version":[{"id":2826,"href":"http:\/\/viplao.com\/index.php\/wp-json\/wp\/v2\/posts\/2823\/revisions\/2826"}],"wp:attachment":[{"href":"http:\/\/viplao.com\/index.php\/wp-json\/wp\/v2\/media?parent=2823"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/viplao.com\/index.php\/wp-json\/wp\/v2\/categories?post=2823"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/viplao.com\/index.php\/wp-json\/wp\/v2\/tags?post=2823"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}