{"id":441642,"date":"2025-05-16T09:42:01","date_gmt":"2025-05-16T01:42:01","guid":{"rendered":"https:\/\/www.idc.net\/help\/?p=441642"},"modified":"2025-05-16T09:42:01","modified_gmt":"2025-05-16T01:42:01","slug":"mysql%e8%b5%8b%e5%80%bc%e8%bf%90%e7%ae%97%e7%ac%a6%e5%85%a8%e9%9d%a2%e8%a7%a3%e6%9e%90%e5%8f%8a%e5%ae%9e%e7%94%a8%e6%a1%88%e4%be%8b%e5%88%86%e4%ba%ab","status":"publish","type":"post","link":"https:\/\/idc.net\/help\/441642\/","title":{"rendered":"MySQL\u8d4b\u503c\u8fd0\u7b97\u7b26\u5168\u9762\u89e3\u6790\u53ca\u5b9e\u7528\u6848\u4f8b\u5206\u4eab"},"content":{"rendered":"<h2>\u5f15\u8a00<\/h2>\n<p>\u5728\u65e5\u5e38\u6570\u636e\u5e93\u7ba1\u7406\u548c\u6570\u636e\u5904\u7406\u5de5\u4f5c\u4e2d\uff0cMySQL\u8d4b\u503c\u8fd0\u7b97\u7b26\u662f\u4e00\u9879\u975e\u5e38\u6838\u5fc3\u7684\u529f\u80fd\u3002\u65e0\u8bba\u662f\u5728\u6570\u636e\u66f4\u65b0\u3001\u53d8\u91cf\u8fd0\u7b97\uff0c\u8fd8\u662f\u6761\u4ef6\u5224\u65ad\u4e2d\uff0c\u5b83\u90fd\u626e\u6f14\u7740\u91cd\u8981\u89d2\u8272\u3002\u672c\u6587\u5c06\u4ece\u5b9e\u6218\u51fa\u53d1\uff0c\u7cfb\u7edf\u8bb2\u89e3MySQL\u8d4b\u503c\u8fd0\u7b97\u7b26\u7684\u4f7f\u7528\u65b9\u5f0f\u4e0e\u6ce8\u610f\u4e8b\u9879\uff0c\u5e76\u901a\u8fc7\u4e00\u7cfb\u5217\u5b9e\u9645\u6848\u4f8b\u5e2e\u52a9\u7528\u6237\u6df1\u5165\u7406\u89e3\u3002\u672c\u6587\u9002\u5408\u9700\u8981\u64cd\u4f5cMySQL\u6570\u636e\u5e93\u7684\u5f00\u53d1\u4eba\u5458\u3001\u8fd0\u7ef4\u5de5\u7a0b\u5e08\uff0c\u4ee5\u53ca\u5728\u9999\u6e2f\u5730\u533a\u90e8\u7f72\u9ad8\u6027\u80fd\u5e94\u7528\u7684\u6280\u672f\u56e2\u961f\u3002\u63a8\u8350\u4f7f\u7528\u9ad8\u7a33\u5b9a\u6027\u3001\u9ad8\u5e26\u5bbd\u7684 \u9999\u6e2f\u72ec\u7acb\u670d\u52a1\u5668 \u6216 \u9999\u6e2f\u4e91\u670d\u52a1\u5668 \u6765\u63d0\u5347\u6570\u636e\u5e93\u5904\u7406\u6548\u7387\u548c\u7f51\u7edc\u54cd\u5e94\u901f\u5ea6\u3002<\/p>\n<h2>\u4e00\u3001MySQL\u8d4b\u503c\u8fd0\u7b97\u7b26\u57fa\u7840\u77e5\u8bc6<\/h2>\n<p>\u5728MySQL\u4e2d\uff0c\u6700\u5e38\u7528\u7684\u8d4b\u503c\u8fd0\u7b97\u7b26\u662f\u7b49\u53f7\uff08=\uff09\uff0c\u5176\u4f5c\u7528\u662f\u5c06\u53f3\u4fa7\u7684\u503c\u8d4b\u7ed9\u5de6\u4fa7\u7684\u5b57\u6bb5\u6216\u53d8\u91cf\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code class=\"language-sql\">SET @count = 100;\r\n<\/code><\/pre>\n<p>\u6b64\u5916\uff0c\u5728\u67d0\u4e9b\u8bed\u5883\u4e2d\uff0c\u4f8b\u5982<code>SELECT<\/code>\u8bed\u53e5\u4e2d\uff0c\u5fc5\u987b\u4f7f\u7528<code>:=<\/code>\u6765\u8d4b\u503c\uff0c\u4ee5\u907f\u514d\u4e0e\u6bd4\u8f83\u8fd0\u7b97\u6df7\u6dc6\u3002<\/p>\n<h2>\u4e8c\u3001\u8d4b\u503c\u8fd0\u7b97\u7b26\u5728\u8868\u64cd\u4f5c\u4e2d\u7684\u4f7f\u7528<\/h2>\n<h3>\u793a\u4f8b\u8868\u7ed3\u6784<\/h3>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u793a\u4f8b\u6570\u636e\u5e93\u53ca\u5176\u8868\u7ed3\u6784\uff0c\u9002\u7528\u4e8e\u5546\u54c1\u7ba1\u7406\u573a\u666f\uff1a<\/p>\n<pre><code class=\"language-sql\">CREATE DATABASE IF NOT EXISTS MallDB;\r\nUSE MallDB;\r\n\r\nCREATE TABLE Product (\r\n    ProductId INT PRIMARY KEY,\r\n    CategoryId INT,\r\n    Name VARCHAR(100),\r\n    Price DECIMAL(10, 2)\r\n);\r\n\r\nINSERT INTO Product VALUES\r\n(1, 1001, '\u534e\u4e3a\u624b\u673a', 4999.00),\r\n(2, 1001, '\u8054\u60f3\u7b14\u8bb0\u672c', 5999.00),\r\n(3, 1002, '\u5ba0\u7269\u8bad\u7ec3\u4e66', 39.90),\r\n(4, 1002, '\u72d7\u72d7\u8425\u517b\u98df\u8c31', 29.90);\r\n<\/code><\/pre>\n<h3>\u793a\u4f8b1\uff1a\u6279\u91cf\u4fee\u6539\u5546\u54c1\u4ef7\u683c<\/h3>\n<p>\u5982\u679c\u6211\u4eec\u9700\u8981\u5bf9\u6240\u6709\u5546\u54c1\u964d\u4ef710%\uff0c\u53ef\u4ee5\u4f7f\u7528\u5982\u4e0b\u8bed\u53e5\uff1a<\/p>\n<pre><code class=\"language-sql\">UPDATE Product SET Price = Price * 0.9;\r\n<\/code><\/pre>\n<p>\u8fd9\u7c7b\u64cd\u4f5c\u5728\u5927\u89c4\u6a21\u7535\u5546\u7cfb\u7edf\u4e2d\u975e\u5e38\u5e38\u89c1\uff0c\u5c24\u5176\u9002\u7528\u4e8e\u5728\u9999\u6e2f\u90e8\u7f72\u7684\u4fc3\u9500\u7cfb\u7edf\uff0c\u901a\u8fc7\u9999\u6e2fvps\u53ef\u4ee5\u83b7\u5f97\u66f4\u5feb\u7684\u66f4\u65b0\u54cd\u5e94\u3002<\/p>\n<h3>\u793a\u4f8b2\uff1a\u7279\u5b9a\u6761\u4ef6\u4e0b\u7684\u8d4b\u503c\u66f4\u65b0<\/h3>\n<p>\u4f8b\u5982\uff0c\u4ec5\u5bf9\u5206\u7c7b\u7f16\u53f7\u4e3a1001\u7684\u5546\u54c1\u63d0\u4ef75%\uff1a<\/p>\n<pre><code class=\"language-sql\">UPDATE Product SET Price = Price * 1.05 WHERE CategoryId = 1001;\r\n<\/code><\/pre>\n<h3>\u793a\u4f8b3\uff1a\u5206\u6761\u4ef6\u52a8\u6001\u66f4\u65b0<\/h3>\n<p>\u901a\u8fc7<code>CASE<\/code>\u8bed\u53e5\uff0c\u5b9e\u73b0\u66f4\u590d\u6742\u7684\u66f4\u65b0\u903b\u8f91\uff1a<\/p>\n<pre><code class=\"language-sql\">UPDATE Product \r\nSET Price = CASE\r\n    WHEN Price &gt;= 1000 THEN Price * 0.92\r\n    ELSE Price * 0.95\r\nEND;\r\n<\/code><\/pre>\n<h2>\u4e09\u3001\u7ed9\u53d8\u91cf\u8d4b\u503c\u7684\u65b9\u5f0f<\/h2>\n<p>MySQL\u652f\u6301\u4e24\u79cd\u4e3b\u8981\u65b9\u5f0f\u4e3a\u53d8\u91cf\u8d4b\u503c\uff1a<\/p>\n<h3>1. \u4f7f\u7528SET\u8bed\u53e5<\/h3>\n<pre><code class=\"language-sql\">SET @discount = 0.85;\r\n<\/code><\/pre>\n<h3>2. \u4f7f\u7528SELECT\u8bed\u53e5\u914d\u5408:=<\/h3>\n<pre><code class=\"language-sql\">SELECT @max_price := MAX(Price) FROM Product;\r\n<\/code><\/pre>\n<h3>\u793a\u4f8b4\uff1a\u7ed3\u5408\u53d8\u91cf\u8c03\u6574\u4ef7\u683c<\/h3>\n<pre><code class=\"language-sql\">-- \u8bbe\u7f6e\u6298\u6263\u7387\r\nSET @rate = 0.8;\r\n\r\n-- \u5e94\u7528\u6298\u6263\r\nUPDATE Product SET Price = Price * @rate;\r\n<\/code><\/pre>\n<h3>\u793a\u4f8b5\uff1a\u67e5\u627e\u6700\u8d35\u5546\u54c1\u5e76\u7279\u6b8a\u5904\u7406<\/h3>\n<pre><code class=\"language-sql\">-- \u83b7\u53d6\u6700\u8d35\u5546\u54c1\u4ef7\u683c\r\nSELECT @top_price := MAX(Price) FROM Product;\r\n\r\n-- \u62538\u6298\r\nUPDATE Product SET Price = Price * 0.8 WHERE Price = @top_price;\r\n<\/code><\/pre>\n<h2>\u56db\u3001\u64cd\u4f5c\u5efa\u8bae\u4e0e\u4f18\u5316\u601d\u8def<\/h2>\n<p>\u5728\u6267\u884c\u8d4b\u503c\u64cd\u4f5c\u65f6\uff0c\u8bf7\u52a1\u5fc5\u9075\u5faa\u4ee5\u4e0b\u5efa\u8bae\uff1a<\/p>\n<ul>\n<li><strong>\u4f7f\u7528WHERE\u9650\u5236\u6761\u4ef6<\/strong>\uff0c\u907f\u514d\u5168\u8868\u8bef\u66f4\u65b0\uff1b<\/li>\n<li><strong>\u53d8\u91cf\u4f5c\u7528\u57df<\/strong>\u4ec5\u9650\u5f53\u524d\u4f1a\u8bdd\uff0c\u4f7f\u7528\u65f6\u6ce8\u610f\u751f\u547d\u5468\u671f\uff1b<\/li>\n<li><strong>\u5148SELECT\u6d4b\u8bd5\uff0c\u518dUPDATE\u6267\u884c<\/strong>\uff0c\u4fdd\u969c\u6570\u636e\u5b89\u5168\uff1b<\/li>\n<li><strong>\u5927\u8868\u66f4\u65b0\u9700\u5206\u6279\u6216\u5728\u4f4e\u5cf0\u65f6\u6bb5\u64cd\u4f5c<\/strong>\uff0c\u4f18\u5316\u6027\u80fd\uff1b<\/li>\n<\/ul>\n<p>\u901a\u8fc7\u8fd9\u4e9b\u63aa\u65bd\uff0c\u53ef\u4ee5\u6709\u6548\u63d0\u5347MySQL\u5728\u5927\u6570\u636e\u5904\u7406\u573a\u666f\u4e0b\u7684\u7a33\u5b9a\u6027\u4e0e\u6548\u7387\u3002\u800c\u90e8\u7f72\u5728\u6211\u4eec\u63d0\u4f9b\u7684\u9999\u6e2f\u4e91\u670d\u52a1\u5668\u4e0a\uff0c\u66f4\u80fd\u5229\u7528\u4f4e\u5ef6\u8fdf\u7f51\u7edc\u8fde\u63a5\uff0c\u4fdd\u969c\u4e1a\u52a1\u9ad8\u6548\u8fd0\u884c\u3002<\/p>\n<h2>\u7ed3\u8bed<\/h2>\n<p>\u638c\u63e1MySQL\u8d4b\u503c\u8fd0\u7b97\u7b26\u7684\u591a\u79cd\u4f7f\u7528\u65b9\u5f0f\uff0c\u4e0d\u4ec5\u53ef\u4ee5\u7b80\u5316SQL\u8bed\u53e5\u903b\u8f91\uff0c\u4e5f\u80fd\u63d0\u5347\u6570\u636e\u64cd\u4f5c\u7684\u7075\u6d3b\u6027\u548c\u6548\u7387\u3002\u65e0\u8bba\u662f\u6279\u91cf\u4ef7\u683c\u8c03\u6574\uff0c\u8fd8\u662f\u53d8\u91cf\u8f85\u52a9\u8ba1\u7b97\uff0c\u719f\u7ec3\u8fd0\u7528\u8d4b\u503c\u64cd\u4f5c\u5c06\u4e3a\u6570\u636e\u5e93\u7ef4\u62a4\u548c\u4e1a\u52a1\u5f00\u53d1\u5e26\u6765\u6781\u5927\u4fbf\u5229\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5bfb\u627e\u6027\u80fd\u51fa\u8272\u3001\u8fde\u63a5\u5feb\u901f\u7684\u670d\u52a1\u5668\u73af\u5883\uff0c\u6211\u4eec\u63d0\u4f9b\u5173\u4e8e<a href=\"https:\/\/idc.net\/\"><strong>\u9999\u6e2fvps<\/strong><\/a>\u3001<strong>\u9999\u6e2f\u4e91\u670d\u52a1\u5668<\/strong>\u4e0e<strong>\u9999\u6e2f\u72ec\u7acb\u670d\u52a1\u5668<\/strong>\u7684\u9ad8\u6027\u4ef7\u6bd4\u65b9\u6848\uff0c\u4e3a\u60a8\u7684\u6570\u636e\u5e93\u7cfb\u7edf\u63d0\u4f9b\u575a\u5b9e\u652f\u6491\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5f15\u8a00 \u5728\u65e5\u5e38\u6570\u636e\u5e93\u7ba1\u7406\u548c\u6570\u636e\u5904\u7406\u5de5\u4f5c\u4e2d\uff0cMySQL\u8d4b\u503c\u8fd0\u7b97\u7b26\u662f\u4e00\u9879\u975e\u5e38\u6838\u5fc3\u7684\u529f\u80fd\u3002\u65e0\u8bba\u662f\u5728\u6570\u636e\u66f4\u65b0\u3001\u53d8\u91cf\u8fd0\u7b97\uff0c [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7038],"tags":[],"class_list":["post-441642","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/posts\/441642","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/comments?post=441642"}],"version-history":[{"count":0,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/posts\/441642\/revisions"}],"wp:attachment":[{"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/media?parent=441642"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/categories?post=441642"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/tags?post=441642"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}