{"id":160775,"date":"2024-11-04T00:54:24","date_gmt":"2024-11-03T16:54:24","guid":{"rendered":"https:\/\/server.hk\/cnblog\/160775\/"},"modified":"2024-11-04T00:54:25","modified_gmt":"2024-11-03T16:54:25","slug":"%e8%b3%87%e6%96%99%e5%ba%ab%e6%95%99%e7%a8%8b%ef%bc%9amysql-%e5%87%bd%e6%95%b8%e7%b0%a1%e4%bb%8b","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/160775\/","title":{"rendered":"\u8cc7\u6599\u5eab\u6559\u7a0b\uff1aMySQL \u51fd\u6578\u7c21\u4ecb"},"content":{"rendered":"<h1 id=\"%e8%b3%87%e6%96%99%e5%ba%ab%e6%95%99%e7%a8%8b%ef%bc%9amysql-%e5%87%bd%e6%95%b8%e7%b0%a1%e4%bb%8b-EcLjITclfz\">\u8cc7\u6599\u5eab\u6559\u7a0b\uff1aMySQL \u51fd\u6578\u7c21\u4ecb<\/h1>\n<p>MySQL \u662f\u4e00\u7a2e\u6d41\u884c\u7684\u958b\u6e90\u95dc\u806f\u5f0f\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\uff0c\u5ee3\u6cdb\u61c9\u7528\u65bc\u5404\u7a2e\u7db2\u7ad9\u548c\u61c9\u7528\u7a0b\u5f0f\u4e2d\u3002\u4f5c\u70ba\u4e00\u500b\u5f37\u5927\u7684\u8cc7\u6599\u5eab\u7cfb\u7d71\uff0cMySQL \u63d0\u4f9b\u4e86\u591a\u7a2e\u5167\u5efa\u51fd\u6578\uff0c\u9019\u4e9b\u51fd\u6578\u53ef\u4ee5\u5e6b\u52a9\u958b\u767c\u8005\u66f4\u6709\u6548\u5730\u8655\u7406\u8cc7\u6599\u3002\u672c\u6587\u5c07\u4ecb\u7d39\u4e00\u4e9b\u5e38\u7528\u7684 MySQL \u51fd\u6578\uff0c\u4e26\u63d0\u4f9b\u76f8\u61c9\u7684\u7bc4\u4f8b\uff0c\u4ee5\u5e6b\u52a9\u8b80\u8005\u66f4\u597d\u5730\u7406\u89e3\u5176\u7528\u6cd5\u3002<\/p>\n<h2 id=\"1-%e5%ad%97%e4%b8%b2%e5%87%bd%e6%95%b8-EcLjITclfz\">1. \u5b57\u4e32\u51fd\u6578<\/h2>\n<p>\u5b57\u4e32\u51fd\u6578\u7528\u65bc\u8655\u7406\u548c\u64cd\u4f5c\u5b57\u4e32\u8cc7\u6599\u3002\u4ee5\u4e0b\u662f\u5e7e\u500b\u5e38\u7528\u7684\u5b57\u4e32\u51fd\u6578\uff1a<\/p>\n<ul>\n<li><code>LENGTH()<\/code>\uff1a\u8fd4\u56de\u5b57\u4e32\u7684\u9577\u5ea6\u3002<\/li>\n<li><code>CONCAT()<\/code>\uff1a\u5c07\u591a\u500b\u5b57\u4e32\u9023\u63a5\u6210\u4e00\u500b\u5b57\u4e32\u3002<\/li>\n<li><code>SUBSTRING()<\/code>\uff1a\u5f9e\u5b57\u4e32\u4e2d\u63d0\u53d6\u5b50\u5b57\u4e32\u3002<\/li>\n<\/ul>\n<p>\u4f8b\u5982\uff0c\u4f7f\u7528 <code>CONCAT()<\/code> \u51fd\u6578\u4f86\u9023\u63a5\u5169\u500b\u5b57\u4e32\uff1a<\/p>\n<pre><code>SELECT CONCAT('Hello', ' ', 'World') AS Greeting;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de\u7d50\u679c\uff1a<code>Hello World<\/code>\u3002<\/p>\n<h2 id=\"2-%e6%95%b8%e5%ad%b8%e5%87%bd%e6%95%b8-EcLjITclfz\">2. \u6578\u5b78\u51fd\u6578<\/h2>\n<p>\u6578\u5b78\u51fd\u6578\u7528\u65bc\u57f7\u884c\u6578\u5b78\u8a08\u7b97\u3002\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u898b\u7684\u6578\u5b78\u51fd\u6578\uff1a<\/p>\n<ul>\n<li><code>ABS()<\/code>\uff1a\u8fd4\u56de\u6578\u5b57\u7684\u7d55\u5c0d\u503c\u3002<\/li>\n<li><code>ROUND()<\/code>\uff1a\u5c0d\u6578\u5b57\u9032\u884c\u56db\u6368\u4e94\u5165\u3002<\/li>\n<li><code>FLOOR()<\/code>\uff1a\u8fd4\u56de\u5c0f\u65bc\u6216\u7b49\u65bc\u6307\u5b9a\u6578\u5b57\u7684\u6700\u5927\u6574\u6578\u3002<\/li>\n<\/ul>\n<p>\u4f8b\u5982\uff0c\u4f7f\u7528 <code>ROUND()<\/code> \u51fd\u6578\u4f86\u56db\u6368\u4e94\u5165\u4e00\u500b\u6578\u5b57\uff1a<\/p>\n<pre><code>SELECT ROUND(123.456, 2) AS RoundedValue;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de\u7d50\u679c\uff1a<code>123.46<\/code>\u3002<\/p>\n<h2 id=\"3-%e6%97%a5%e6%9c%9f%e5%92%8c%e6%99%82%e9%96%93%e5%87%bd%e6%95%b8-EcLjITclfz\">3. \u65e5\u671f\u548c\u6642\u9593\u51fd\u6578<\/h2>\n<p>\u65e5\u671f\u548c\u6642\u9593\u51fd\u6578\u7528\u65bc\u8655\u7406\u65e5\u671f\u548c\u6642\u9593\u8cc7\u6599\u3002\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u7528\u7684\u65e5\u671f\u548c\u6642\u9593\u51fd\u6578\uff1a<\/p>\n<ul>\n<li><code>NOW()<\/code>\uff1a\u8fd4\u56de\u7576\u524d\u7684\u65e5\u671f\u548c\u6642\u9593\u3002<\/li>\n<li><code>CURDATE()<\/code>\uff1a\u8fd4\u56de\u7576\u524d\u7684\u65e5\u671f\u3002<\/li>\n<li><code>DATEDIFF()<\/code>\uff1a\u8a08\u7b97\u5169\u500b\u65e5\u671f\u4e4b\u9593\u7684\u5dee\u7570\u3002<\/li>\n<\/ul>\n<p>\u4f8b\u5982\uff0c\u4f7f\u7528 <code>DATEDIFF()<\/code> \u51fd\u6578\u4f86\u8a08\u7b97\u5169\u500b\u65e5\u671f\u4e4b\u9593\u7684\u5929\u6578\uff1a<\/p>\n<pre><code>SELECT DATEDIFF('2023-10-01', '2023-09-01') AS DateDifference;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de\u7d50\u679c\uff1a<code>30<\/code>\u3002<\/p>\n<h2 id=\"4-%e8%81%9a%e5%90%88%e5%87%bd%e6%95%b8-EcLjITclfz\">4. \u805a\u5408\u51fd\u6578<\/h2>\n<p>\u805a\u5408\u51fd\u6578\u7528\u65bc\u5c0d\u8cc7\u6599\u9032\u884c\u8a08\u7b97\uff0c\u4e26\u8fd4\u56de\u55ae\u4e00\u503c\u3002\u5e38\u898b\u7684\u805a\u5408\u51fd\u6578\u5305\u62ec\uff1a<\/p>\n<ul>\n<li><code>COUNT()<\/code>\uff1a\u8a08\u7b97\u884c\u6578\u3002<\/li>\n<li><code>SUM()<\/code>\uff1a\u8a08\u7b97\u6578\u503c\u7684\u7e3d\u548c\u3002<\/li>\n<li><code>AVG()<\/code>\uff1a\u8a08\u7b97\u6578\u503c\u7684\u5e73\u5747\u503c\u3002<\/li>\n<\/ul>\n<p>\u4f8b\u5982\uff0c\u4f7f\u7528 <code>SUM()<\/code> \u51fd\u6578\u4f86\u8a08\u7b97\u67d0\u4e00\u5217\u7684\u7e3d\u548c\uff1a<\/p>\n<pre><code>SELECT SUM(price) AS TotalPrice FROM products;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de\u6240\u6709\u7522\u54c1\u50f9\u683c\u7684\u7e3d\u548c\u3002<\/p>\n<h2 id=\"5-%e6%a2%9d%e4%bb%b6%e5%87%bd%e6%95%b8-EcLjITclfz\">5. \u689d\u4ef6\u51fd\u6578<\/h2>\n<p>\u689d\u4ef6\u51fd\u6578\u7528\u65bc\u6839\u64da\u7279\u5b9a\u689d\u4ef6\u8fd4\u56de\u4e0d\u540c\u7684\u503c\u3002\u6700\u5e38\u7528\u7684\u689d\u4ef6\u51fd\u6578\u662f <code>IF()<\/code> \u548c <code>CASE<\/code>\u3002<\/p>\n<p>\u4f8b\u5982\uff0c\u4f7f\u7528 <code>IF()<\/code> \u51fd\u6578\u4f86\u6839\u64da\u689d\u4ef6\u8fd4\u56de\u4e0d\u540c\u7684\u7d50\u679c\uff1a<\/p>\n<pre><code>SELECT IF(score &gt;= 60, '\u53ca\u683c', '\u4e0d\u53ca\u683c') AS Result FROM students;<\/code><\/pre>\n<p>\u9019\u5c07\u6839\u64da\u5b78\u751f\u7684\u5206\u6578\u8fd4\u56de\u201c\u53ca\u683c\u201d\u6216\u201c\u4e0d\u53ca\u683c\u201d\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-EcLjITclfz\">\u7e3d\u7d50<\/h2>\n<p>MySQL \u63d0\u4f9b\u4e86\u591a\u7a2e\u51fd\u6578\uff0c\u5e6b\u52a9\u958b\u767c\u8005\u5728\u8cc7\u6599\u5eab\u64cd\u4f5c\u4e2d\u63d0\u9ad8\u6548\u7387\u3002\u7121\u8ad6\u662f\u5b57\u4e32\u8655\u7406\u3001\u6578\u5b78\u8a08\u7b97\u3001\u65e5\u671f\u6642\u9593\u7ba1\u7406\u9084\u662f\u8cc7\u6599\u805a\u5408\uff0c\u9019\u4e9b\u51fd\u6578\u90fd\u80fd\u5920\u7c21\u5316\u958b\u767c\u904e\u7a0b\u3002\u4e86\u89e3\u4e26\u638c\u63e1\u9019\u4e9b\u51fd\u6578\u7684\u4f7f\u7528\uff0c\u5c07\u6709\u52a9\u65bc\u63d0\u5347\u8cc7\u6599\u5eab\u64cd\u4f5c\u7684\u9748\u6d3b\u6027\u548c\u6548\u7387\u3002<\/p>\n<p>\u5982\u679c\u60a8\u5c0d\u65bc\u8cc7\u6599\u5eab\u7ba1\u7406\u6709\u9032\u4e00\u6b65\u7684\u9700\u6c42\uff0c\u8003\u616e\u4f7f\u7528 <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u670d\u52d9\u4f86\u642d\u5efa\u60a8\u7684\u8cc7\u6599\u5eab\u74b0\u5883\uff0c\u4eab\u53d7\u7a69\u5b9a\u548c\u9ad8\u6548\u7684\u6027\u80fd\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22MySQL\u51fd\u6578\u7684\u57fa\u672c\u6982\u5ff5\u8207\u61c9\u7528\uff0c\u5b78\u7fd2\u5982\u4f55\u6709\u6548\u7ba1\u7406\u548c\u64cd\u4f5c\u8cc7\u6599\u5eab\uff0c\u63d0\u5347\u4f60\u7684\u8cc7\u6599\u5eab\u6280\u80fd\u3002<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-160775","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160775","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=160775"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160775\/revisions"}],"predecessor-version":[{"id":160776,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160775\/revisions\/160776"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=160775"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=160775"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=160775"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}