{"id":196420,"date":"2024-11-13T23:26:20","date_gmt":"2024-11-13T15:26:20","guid":{"rendered":"https:\/\/server.hk\/cnblog\/196420\/"},"modified":"2024-11-13T23:26:22","modified_gmt":"2024-11-13T15:26:22","slug":"%e5%80%bc%e7%9a%84sql%e8%aa%9e%e5%8f%a5-%e6%9f%a5%e7%9c%8b%e6%95%b8%e6%93%9a%e5%ba%ab%e6%9b%b4%e5%a4%a7","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/196420\/","title":{"rendered":"\u503c\u7684SQL\u8a9e\u53e5 (\u67e5\u770b\u6578\u64da\u5eab\u66f4\u5927)"},"content":{"rendered":"<h1 id=\"%e5%80%bc%e7%9a%84sql%e8%aa%9e%e5%8f%a5-%e6%9f%a5%e7%9c%8b%e6%95%b8%e6%93%9a%e5%ba%ab%e6%9b%b4%e5%a4%a7-XnGLdNtIAP\">\u503c\u7684SQL\u8a9e\u53e5 (\u67e5\u770b\u6578\u64da\u5eab\u66f4\u5927)<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0cSQL\uff08\u7d50\u69cb\u5316\u67e5\u8a62\u8a9e\u8a00\uff09\u662f\u4e00\u7a2e\u81f3\u95dc\u91cd\u8981\u7684\u5de5\u5177\u3002\u7121\u8ad6\u662f\u67e5\u8a62\u6578\u64da\u3001\u66f4\u65b0\u8a18\u9304\u9084\u662f\u7ba1\u7406\u6578\u64da\u5eab\u7d50\u69cb\uff0cSQL\u90fd\u80fd\u63d0\u4f9b\u5f37\u5927\u7684\u652f\u6301\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u4e00\u4e9b\u6709\u7528\u7684SQL\u8a9e\u53e5\uff0c\u5e6b\u52a9\u7528\u6236\u66f4\u6709\u6548\u5730\u67e5\u770b\u548c\u7ba1\u7406\u6578\u64da\u5eab\u4e2d\u7684\u6578\u64da\u3002<\/p>\n<h2 id=\"1-%e5%9f%ba%e6%9c%ac%e6%9f%a5%e8%a9%a2%e8%aa%9e%e5%8f%a5-XnGLdNtIAP\">1. \u57fa\u672c\u67e5\u8a62\u8a9e\u53e5<\/h2>\n<p>\u6700\u57fa\u672c\u7684SQL\u67e5\u8a62\u8a9e\u53e5\u662fSELECT\u8a9e\u53e5\u3002\u9019\u500b\u8a9e\u53e5\u7528\u65bc\u5f9e\u6578\u64da\u5eab\u4e2d\u6aa2\u7d22\u6578\u64da\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u7c21\u55ae\u7684\u4f8b\u5b50\uff1a<\/p>\n<pre><code>SELECT * FROM users;<\/code><\/pre>\n<p>\u9019\u689d\u8a9e\u53e5\u5c07\u5f9e\u540d\u70ba\u201cusers\u201d\u7684\u8868\u4e2d\u6aa2\u7d22\u6240\u6709\u5217\u7684\u6240\u6709\u8a18\u9304\u3002\u4f7f\u7528\u201c*\u201d\u7b26\u865f\u8868\u793a\u9078\u64c7\u6240\u6709\u5217\u3002\u5982\u679c\u53ea\u60f3\u9078\u64c7\u7279\u5b9a\u7684\u5217\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n<pre><code>SELECT username, email FROM users;<\/code><\/pre>\n<h2 id=\"2-%e4%bd%bf%e7%94%a8where%e5%ad%90%e5%8f%a5%e9%81%8e%e6%bf%be%e6%95%b8%e6%93%9a-XnGLdNtIAP\">2. \u4f7f\u7528WHERE\u5b50\u53e5\u904e\u6ffe\u6578\u64da<\/h2>\n<p>\u5728\u67e5\u8a62\u6578\u64da\u6642\uff0c\u7d93\u5e38\u9700\u8981\u6839\u64da\u7279\u5b9a\u689d\u4ef6\u904e\u6ffe\u7d50\u679c\u3002\u9019\u6642\u53ef\u4ee5\u4f7f\u7528WHERE\u5b50\u53e5\u3002\u4f8b\u5982\uff0c\u82e5\u8981\u67e5\u8a62\u6240\u6709\u5e74\u9f61\u5927\u65bc30\u7684\u7528\u6236\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u8a9e\u53e5\uff1a<\/p>\n<pre><code>SELECT * FROM users WHERE age &gt; 30;<\/code><\/pre>\n<p>\u9019\u6a23\u53ef\u4ee5\u6709\u6548\u5730\u7e2e\u5c0f\u67e5\u8a62\u7bc4\u570d\uff0c\u50c5\u8fd4\u56de\u7b26\u5408\u689d\u4ef6\u7684\u8a18\u9304\u3002<\/p>\n<h2 id=\"3-%e6%8e%92%e5%ba%8f%e6%9f%a5%e8%a9%a2%e7%b5%90%e6%9e%9c-XnGLdNtIAP\">3. \u6392\u5e8f\u67e5\u8a62\u7d50\u679c<\/h2>\n<p>\u6709\u6642\u5019\uff0c\u67e5\u8a62\u7d50\u679c\u9700\u8981\u6309\u7167\u7279\u5b9a\u7684\u9806\u5e8f\u986f\u793a\u3002\u53ef\u4ee5\u4f7f\u7528ORDER BY\u5b50\u53e5\u4f86\u5be6\u73fe\u3002\u4f8b\u5982\uff0c\u82e5\u8981\u6309\u5e74\u9f61\u5347\u5e8f\u6392\u5217\u7528\u6236\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n<pre><code>SELECT * FROM users ORDER BY age ASC;<\/code><\/pre>\n<p>\u5982\u679c\u9700\u8981\u6309\u5e74\u9f61\u964d\u5e8f\u6392\u5217\uff0c\u53ea\u9700\u5c07\u201cASC\u201d\u6539\u70ba\u201cDESC\u201d\u5373\u53ef\uff1a<\/p>\n<pre><code>SELECT * FROM users ORDER BY age DESC;<\/code><\/pre>\n<h2 id=\"4-%e9%99%90%e5%88%b6%e6%9f%a5%e8%a9%a2%e7%b5%90%e6%9e%9c%e7%9a%84%e6%95%b8%e9%87%8f-XnGLdNtIAP\">4. \u9650\u5236\u67e5\u8a62\u7d50\u679c\u7684\u6578\u91cf<\/h2>\n<p>\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u67e5\u8a62\u7d50\u679c\u53ef\u80fd\u6703\u8fd4\u56de\u5927\u91cf\u6578\u64da\u3002\u70ba\u4e86\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\uff0c\u53ef\u4ee5\u4f7f\u7528LIMIT\u5b50\u53e5\u4f86\u9650\u5236\u8fd4\u56de\u7684\u8a18\u9304\u6578\u91cf\u3002\u4f8b\u5982\uff0c\u82e5\u53ea\u60f3\u67e5\u770b\u524d10\u689d\u8a18\u9304\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n<pre><code>SELECT * FROM users LIMIT 10;<\/code><\/pre>\n<h2 id=\"5-%e8%81%9a%e5%90%88%e5%87%bd%e6%95%b8%e7%9a%84%e4%bd%bf%e7%94%a8-XnGLdNtIAP\">5. \u805a\u5408\u51fd\u6578\u7684\u4f7f\u7528<\/h2>\n<p>SQL\u9084\u63d0\u4f9b\u4e86\u591a\u7a2e\u805a\u5408\u51fd\u6578\uff0c\u5982COUNT\u3001SUM\u3001AVG\u7b49\uff0c\u7528\u65bc\u8a08\u7b97\u6578\u64da\u7684\u7d71\u8a08\u4fe1\u606f\u3002\u4f8b\u5982\uff0c\u82e5\u8981\u8a08\u7b97\u7528\u6236\u7684\u7e3d\u6578\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u8a9e\u53e5\uff1a<\/p>\n<pre><code>SELECT COUNT(*) FROM users;<\/code><\/pre>\n<p>\u5982\u679c\u60f3\u8981\u8a08\u7b97\u7528\u6236\u5e74\u9f61\u7684\u5e73\u5747\u503c\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n<pre><code>SELECT AVG(age) FROM users;<\/code><\/pre>\n<h2 id=\"6-%e5%88%86%e7%b5%84%e6%9f%a5%e8%a9%a2-XnGLdNtIAP\">6. \u5206\u7d44\u67e5\u8a62<\/h2>\n<p>\u5728\u9032\u884c\u6578\u64da\u5206\u6790\u6642\uff0c\u7d93\u5e38\u9700\u8981\u5c0d\u6578\u64da\u9032\u884c\u5206\u7d44\u3002\u53ef\u4ee5\u4f7f\u7528GROUP BY\u5b50\u53e5\u4f86\u5be6\u73fe\u3002\u4f8b\u5982\uff0c\u82e5\u8981\u6309\u6027\u5225\u7d71\u8a08\u7528\u6236\u6578\u91cf\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n<pre><code>SELECT gender, COUNT(*) FROM users GROUP BY gender;<\/code><\/pre>\n<h2 id=\"7-%e9%80%a3%e6%8e%a5%e5%a4%9a%e5%80%8b%e8%a1%a8-XnGLdNtIAP\">7. \u9023\u63a5\u591a\u500b\u8868<\/h2>\n<p>\u5728\u5be6\u969b\u61c9\u7528\u4e2d\uff0c\u6578\u64da\u901a\u5e38\u5206\u4f48\u5728\u591a\u500b\u8868\u4e2d\u3002\u53ef\u4ee5\u4f7f\u7528JOIN\u8a9e\u53e5\u4f86\u9023\u63a5\u9019\u4e9b\u8868\u3002\u4f8b\u5982\uff0c\u82e5\u8981\u67e5\u8a62\u7528\u6236\u53ca\u5176\u8a02\u55ae\u4fe1\u606f\uff0c\u53ef\u4ee5\u4f7f\u7528INNER JOIN\uff1a<\/p>\n<pre><code>SELECT users.username, orders.order_id \nFROM users \nINNER JOIN orders ON users.id = orders.user_id;<\/code><\/pre>\n<h2 id=\"%e7%b8%bd%e7%b5%90-XnGLdNtIAP\">\u7e3d\u7d50<\/h2>\n<p>\u638c\u63e1\u9019\u4e9b\u57fa\u672c\u7684SQL\u8a9e\u53e5\u53ef\u4ee5\u5e6b\u52a9\u7528\u6236\u66f4\u6709\u6548\u5730\u67e5\u770b\u548c\u7ba1\u7406\u6578\u64da\u5eab\u4e2d\u7684\u6578\u64da\u3002\u7121\u8ad6\u662f\u9032\u884c\u7c21\u55ae\u7684\u67e5\u8a62\u9084\u662f\u8907\u96dc\u7684\u6578\u64da\u5206\u6790\uff0c\u9019\u4e9b\u8a9e\u53e5\u90fd\u662f\u4e0d\u53ef\u6216\u7f3a\u7684\u5de5\u5177\u3002\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u8655\u7406\u7684\u7528\u6236\uff0c\u9078\u64c7\u5408\u9069\u7684<a href=\"https:\/\/server.hk\">VPS<\/a>\u6216<a href=\"https:\/\/server.hk\">\u9999\u6e2f\u4f3a\u670d\u5668<\/a>\u53ef\u4ee5\u63d0\u4f9b\u66f4\u597d\u7684\u6027\u80fd\u548c\u7a69\u5b9a\u6027\uff0c\u9032\u4e00\u6b65\u63d0\u5347\u6578\u64da\u5eab\u7ba1\u7406\u7684\u6548\u7387\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22\u6709\u6548\u7684SQL\u8a9e\u53e5\uff0c\u63d0\u5347\u6578\u64da\u5eab\u67e5\u8a62\u6548\u7387\uff0c\u8f15\u9b06\u67e5\u770b\u548c\u7ba1\u7406\u66f4\u5927\u6578\u64da\u96c6\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-196420","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/196420","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=196420"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/196420\/revisions"}],"predecessor-version":[{"id":196421,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/196420\/revisions\/196421"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=196420"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=196420"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=196420"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}