{"id":168031,"date":"2024-11-06T08:56:23","date_gmt":"2024-11-06T00:56:23","guid":{"rendered":"https:\/\/server.hk\/cnblog\/168031\/"},"modified":"2024-11-06T08:56:23","modified_gmt":"2024-11-06T00:56:23","slug":"%e8%81%8a%e4%b8%80%e8%81%8a-mysql-%e7%9b%b8%e9%97%9c%e5%ad%90%e6%9f%a5%e8%a9%a2","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/168031\/","title":{"rendered":"\u804a\u4e00\u804a MySQL \u76f8\u95dc\u5b50\u67e5\u8a62"},"content":{"rendered":"<h1 id=\"%e8%81%8a%e4%b8%80%e8%81%8a-mysql-%e7%9b%b8%e9%97%9c%e5%ad%90%e6%9f%a5%e8%a9%a2-QxSXsAcDEu\">\u804a\u4e00\u804a MySQL \u76f8\u95dc\u5b50\u67e5\u8a62<\/h1>\n<p>\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0cMySQL \u662f\u4e00\u500b\u5ee3\u6cdb\u4f7f\u7528\u7684\u958b\u6e90\u95dc\u806f\u5f0f\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u3002\u5b83\u7684\u5f37\u5927\u529f\u80fd\u4e4b\u4e00\u5c31\u662f\u652f\u63f4\u5b50\u67e5\u8a62\uff08Subquery\uff09\uff0c\u9019\u662f\u4e00\u7a2e\u5728 SQL \u67e5\u8a62\u4e2d\u5d4c\u5957\u5176\u4ed6\u67e5\u8a62\u7684\u6280\u8853\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e MySQL \u4e2d\u7684\u5b50\u67e5\u8a62\uff0c\u5305\u62ec\u5176\u985e\u578b\u3001\u4f7f\u7528\u60c5\u5883\u53ca\u7bc4\u4f8b\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%af%e5%ad%90%e6%9f%a5%e8%a9%a2%ef%bc%9f-QxSXsAcDEu\">\u4ec0\u9ebc\u662f\u5b50\u67e5\u8a62\uff1f<\/h2>\n<p>\u5b50\u67e5\u8a62\u662f\u6307\u5728\u4e00\u500b SQL \u67e5\u8a62\u4e2d\u5d4c\u5165\u53e6\u4e00\u500b\u67e5\u8a62\u3002\u9019\u7a2e\u67e5\u8a62\u53ef\u4ee5\u7528\u65bc\u9078\u64c7\u3001\u63d2\u5165\u3001\u66f4\u65b0\u6216\u522a\u9664\u8cc7\u6599\u3002\u5b50\u67e5\u8a62\u901a\u5e38\u7528\u65bc\u9700\u8981\u5f9e\u8cc7\u6599\u5eab\u4e2d\u7372\u53d6\u984d\u5916\u8cc7\u8a0a\u7684\u60c5\u6cc1\uff0c\u4e26\u4e14\u53ef\u4ee5\u4f7f\u67e5\u8a62\u66f4\u52a0\u9748\u6d3b\u548c\u5f37\u5927\u3002<\/p>\n<h2 id=\"%e5%ad%90%e6%9f%a5%e8%a9%a2%e7%9a%84%e9%a1%9e%e5%9e%8b-QxSXsAcDEu\">\u5b50\u67e5\u8a62\u7684\u985e\u578b<\/h2>\n<p>\u5728 MySQL \u4e2d\uff0c\u5b50\u67e5\u8a62\u4e3b\u8981\u6709\u4ee5\u4e0b\u5e7e\u7a2e\u985e\u578b\uff1a<\/p>\n<ul>\n<li><strong>\u55ae\u884c\u5b50\u67e5\u8a62\uff1a<\/strong>\u8fd4\u56de\u55ae\u4e00\u884c\u7684\u7d50\u679c\uff0c\u901a\u5e38\u7528\u65bc\u6bd4\u8f03\u904b\u7b97\u3002<\/li>\n<li><strong>\u591a\u884c\u5b50\u67e5\u8a62\uff1a<\/strong>\u8fd4\u56de\u591a\u884c\u7684\u7d50\u679c\uff0c\u901a\u5e38\u7528\u65bc IN \u6216 EXISTS \u5b50\u53e5\u4e2d\u3002<\/li>\n<li><strong>\u76f8\u95dc\u5b50\u67e5\u8a62\uff1a<\/strong>\u9019\u7a2e\u5b50\u67e5\u8a62\u4f9d\u8cf4\u65bc\u5916\u90e8\u67e5\u8a62\u7684\u7d50\u679c\uff0c\u901a\u5e38\u5728 WHERE \u5b50\u53e5\u4e2d\u4f7f\u7528\u3002<\/li>\n<li><strong>\u975e\u76f8\u95dc\u5b50\u67e5\u8a62\uff1a<\/strong>\u9019\u7a2e\u5b50\u67e5\u8a62\u4e0d\u4f9d\u8cf4\u65bc\u5916\u90e8\u67e5\u8a62\uff0c\u53ef\u4ee5\u7368\u7acb\u57f7\u884c\u3002<\/li>\n<\/ul>\n<h2 id=\"%e5%ad%90%e6%9f%a5%e8%a9%a2%e7%9a%84%e4%bd%bf%e7%94%a8%e6%83%85%e5%a2%83-QxSXsAcDEu\">\u5b50\u67e5\u8a62\u7684\u4f7f\u7528\u60c5\u5883<\/h2>\n<p>\u5b50\u67e5\u8a62\u53ef\u4ee5\u7528\u65bc\u591a\u7a2e\u60c5\u5883\uff0c\u4f8b\u5982\uff1a<\/p>\n<ul>\n<li>\u5f9e\u4e00\u500b\u8868\u4e2d\u9078\u64c7\u8cc7\u6599\uff0c\u4e26\u6839\u64da\u53e6\u4e00\u500b\u8868\u7684\u7d50\u679c\u9032\u884c\u904e\u6ffe\u3002<\/li>\n<li>\u8a08\u7b97\u805a\u5408\u51fd\u6578\u7684\u7d50\u679c\uff0c\u4e26\u6839\u64da\u8a72\u7d50\u679c\u9032\u884c\u7be9\u9078\u3002<\/li>\n<li>\u5728\u63d2\u5165\u6216\u66f4\u65b0\u64cd\u4f5c\u4e2d\u4f7f\u7528\u5b50\u67e5\u8a62\u4f86\u7372\u53d6\u9700\u8981\u7684\u503c\u3002<\/li>\n<\/ul>\n<h2 id=\"%e5%ad%90%e6%9f%a5%e8%a9%a2%e7%9a%84%e7%af%84%e4%be%8b-QxSXsAcDEu\">\u5b50\u67e5\u8a62\u7684\u7bc4\u4f8b<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e9b MySQL \u5b50\u67e5\u8a62\u7684\u7bc4\u4f8b\uff1a<\/p>\n<h3 id=\"%e7%af%84%e4%be%8b-1%ef%bc%9a%e5%96%ae%e8%a1%8c%e5%ad%90%e6%9f%a5%e8%a9%a2-QxSXsAcDEu\">\u7bc4\u4f8b 1\uff1a\u55ae\u884c\u5b50\u67e5\u8a62<\/h3>\n<pre><code>SELECT name \nFROM employees \nWHERE salary = (SELECT MAX(salary) FROM employees);<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07\u8fd4\u56de\u85aa\u6c34\u6700\u9ad8\u7684\u54e1\u5de5\u7684\u59d3\u540d\u3002<\/p>\n<h3 id=\"%e7%af%84%e4%be%8b-2%ef%bc%9a%e5%a4%9a%e8%a1%8c%e5%ad%90%e6%9f%a5%e8%a9%a2-QxSXsAcDEu\">\u7bc4\u4f8b 2\uff1a\u591a\u884c\u5b50\u67e5\u8a62<\/h3>\n<pre><code>SELECT name \nFROM employees \nWHERE department_id IN (SELECT id FROM departments WHERE location = 'Hong Kong');<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07\u8fd4\u56de\u4f4d\u65bc\u9999\u6e2f\u7684\u6240\u6709\u90e8\u9580\u4e2d\u7684\u54e1\u5de5\u59d3\u540d\u3002<\/p>\n<h3 id=\"%e7%af%84%e4%be%8b-3%ef%bc%9a%e7%9b%b8%e9%97%9c%e5%ad%90%e6%9f%a5%e8%a9%a2-QxSXsAcDEu\">\u7bc4\u4f8b 3\uff1a\u76f8\u95dc\u5b50\u67e5\u8a62<\/h3>\n<pre><code>SELECT e1.name \nFROM employees e1 \nWHERE e1.salary &gt; (SELECT AVG(salary) FROM employees e2 WHERE e1.department_id = e2.department_id);<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07\u8fd4\u56de\u6bcf\u500b\u90e8\u9580\u4e2d\u85aa\u6c34\u9ad8\u65bc\u8a72\u90e8\u9580\u5e73\u5747\u85aa\u6c34\u7684\u54e1\u5de5\u59d3\u540d\u3002<\/p>\n<h2 id=\"%e6%b3%a8%e6%84%8f%e4%ba%8b%e9%a0%85-QxSXsAcDEu\">\u6ce8\u610f\u4e8b\u9805<\/h2>\n<p>\u96d6\u7136\u5b50\u67e5\u8a62\u975e\u5e38\u5f37\u5927\uff0c\u4f46\u5728\u4f7f\u7528\u6642\u9700\u8981\u6ce8\u610f\u4ee5\u4e0b\u5e7e\u9ede\uff1a<\/p>\n<ul>\n<li>\u6027\u80fd\uff1a\u5b50\u67e5\u8a62\u53ef\u80fd\u6703\u5f71\u97ff\u67e5\u8a62\u6027\u80fd\uff0c\u7279\u5225\u662f\u5728\u8655\u7406\u5927\u91cf\u8cc7\u6599\u6642\u3002\u8003\u616e\u4f7f\u7528 JOIN \u4f86\u66ff\u4ee3\u67d0\u4e9b\u5b50\u67e5\u8a62\u3002<\/li>\n<li>\u53ef\u8b80\u6027\uff1a\u904e\u591a\u7684\u5d4c\u5957\u67e5\u8a62\u53ef\u80fd\u6703\u4f7f SQL \u8a9e\u53e5\u8b8a\u5f97\u96e3\u4ee5\u7406\u89e3\uff0c\u61c9\u9069\u5ea6\u4f7f\u7528\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b8%bd%e7%b5%90-QxSXsAcDEu\">\u7e3d\u7d50<\/h2>\n<p>MySQL \u7684\u5b50\u67e5\u8a62\u529f\u80fd\u70ba\u8cc7\u6599\u67e5\u8a62\u63d0\u4f9b\u4e86\u9748\u6d3b\u6027\u548c\u5f37\u5927\u6027\u3002\u7121\u8ad6\u662f\u55ae\u884c\u9084\u662f\u591a\u884c\u5b50\u67e5\u8a62\uff0c\u6b63\u78ba\u4f7f\u7528\u90fd\u80fd\u63d0\u9ad8\u67e5\u8a62\u7684\u6548\u7387\u548c\u53ef\u8b80\u6027\u3002\u5728\u9078\u64c7\u4f7f\u7528\u5b50\u67e5\u8a62\u6642\uff0c\u958b\u767c\u8005\u61c9\u8003\u616e\u6027\u80fd\u548c\u53ef\u8b80\u6027\uff0c\u4ee5\u78ba\u4fdd\u6700\u4f73\u7684\u8cc7\u6599\u5eab\u64cd\u4f5c\u9ad4\u9a57\u3002\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> \u4f86\u642d\u5efa\u60a8\u7684 MySQL \u74b0\u5883\uff0c\u4eab\u53d7\u7a69\u5b9a\u548c\u9ad8\u6548\u7684\u670d\u52d9\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22 MySQL \u4e2d\u7684\u5b50\u67e5\u8a62\uff0c\u4e86\u89e3\u5176\u7528\u6cd5\u3001\u985e\u578b\u53ca\u6700\u4f73\u5be6\u8e10\uff0c\u63d0\u5347\u6578\u64da\u67e5\u8a62\u6548\u7387\u8207\u9748\u6d3b\u6027\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-168031","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168031","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=168031"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168031\/revisions"}],"predecessor-version":[{"id":168032,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168031\/revisions\/168032"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=168031"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=168031"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=168031"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}