{"id":75670,"date":"2024-10-16T00:14:35","date_gmt":"2024-10-15T16:14:35","guid":{"rendered":"https:\/\/server.hk\/cnblog\/75670\/"},"modified":"2024-10-16T00:14:35","modified_gmt":"2024-10-15T16:14:35","slug":"mysql%ef%bc%9a%e5%8f%96%e5%87%ba%e5%94%af%e4%b8%80%e5%80%bc%e7%9a%84%e6%95%b8%e6%93%9a%e5%ba%ab%e6%aa%a2%e7%b4%a2%e6%8a%80%e5%b7%a7-mysql%e5%8f%96%e6%9f%90%e5%80%bc%e5%94%af%e4%b8%80%e6%95%b8","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/75670\/","title":{"rendered":"MySQL\uff1a\u53d6\u51fa\u552f\u4e00\u503c\u7684\u6578\u64da\u5eab\u6aa2\u7d22\u6280\u5de7 (MySQL\u53d6\u67d0\u503c\u552f\u4e00\u6578\u64da\u5eab)"},"content":{"rendered":"

MySQL\uff1a\u53d6\u51fa\u552f\u4e00\u503c\u7684\u6578\u64da\u5eab\u6aa2\u7d22\u6280\u5de7<\/h1>\n

\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0cMySQL\u662f\u4e00\u500b\u5ee3\u6cdb\u4f7f\u7528\u7684\u95dc\u806f\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\u3002\u7576\u6211\u5011\u9700\u8981\u5f9e\u6578\u64da\u5eab\u4e2d\u6aa2\u7d22\u552f\u4e00\u503c\u6642\uff0cMySQL\u63d0\u4f9b\u4e86\u591a\u7a2e\u65b9\u6cd5\u4f86\u9054\u6210\u9019\u4e00\u76ee\u6a19\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5982\u4f55\u6709\u6548\u5730\u4f7f\u7528MySQL\u4f86\u53d6\u51fa\u552f\u4e00\u503c\uff0c\u4e26\u63d0\u4f9b\u4e00\u4e9b\u5be6\u7528\u7684\u7bc4\u4f8b\u548c\u6280\u5de7\u3002<\/p>\n

\u70ba\u4ec0\u9ebc\u9700\u8981\u552f\u4e00\u503c\uff1f<\/h2>\n

\u5728\u6578\u64da\u5eab\u4e2d\uff0c\u552f\u4e00\u503c\u7684\u6aa2\u7d22\u901a\u5e38\u662f\u70ba\u4e86\u907f\u514d\u91cd\u8907\u6578\u64da\uff0c\u78ba\u4fdd\u6578\u64da\u7684\u5b8c\u6574\u6027\u548c\u6e96\u78ba\u6027\u3002\u4f8b\u5982\uff0c\u5728\u7528\u6236\u8cc7\u6599\u8868\u4e2d\uff0c\u6211\u5011\u53ef\u80fd\u5e0c\u671b\u7372\u53d6\u6240\u6709\u4e0d\u540c\u7684\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\uff0c\u4ee5\u4fbf\u9032\u884c\u90f5\u4ef6\u63a8\u5ee3\u6216\u7528\u6236\u5206\u6790\u3002<\/p>\n

\u4f7f\u7528DISTINCT\u95dc\u9375\u5b57<\/h2>\n

MySQL\u4e2d\u6700\u5e38\u7528\u7684\u6aa2\u7d22\u552f\u4e00\u503c\u7684\u65b9\u6cd5\u662f\u4f7f\u7528DISTINCT<\/strong>\u95dc\u9375\u5b57\u3002\u9019\u500b\u95dc\u9375\u5b57\u53ef\u4ee5\u7528\u4f86\u5f9e\u67e5\u8a62\u7d50\u679c\u4e2d\u6392\u9664\u91cd\u8907\u7684\u884c\u3002<\/p>\n

SELECT DISTINCT column_name FROM table_name;<\/code><\/pre>\n
\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70bausers<\/strong>\u7684\u8868\uff0c\u4e26\u4e14\u6211\u5011\u60f3\u8981\u7372\u53d6\u6240\u6709\u4e0d\u540c\u7684\u570b\u5bb6\uff1a<\/p>\n
SELECT DISTINCT country FROM users;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56deusers<\/strong>\u8868\u4e2d\u6240\u6709\u552f\u4e00\u7684\u570b\u5bb6\u540d\u7a31\u3002<\/p>\n
\u7d50\u5408GROUP BY\u4f7f\u7528<\/h2>\n
\u53e6\u4e00\u7a2e\u7372\u53d6\u552f\u4e00\u503c\u7684\u65b9\u6cd5\u662f\u4f7f\u7528GROUP BY<\/strong>\u5b50\u53e5\u3002\u9019\u500b\u5b50\u53e5\u4e0d\u50c5\u53ef\u4ee5\u7528\u4f86\u7372\u53d6\u552f\u4e00\u503c\uff0c\u9084\u53ef\u4ee5\u9032\u884c\u805a\u5408\u8a08\u7b97\u3002<\/p>\n
SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name;<\/code><\/pre>\n
\u4f8b\u5982\uff0c\u5982\u679c\u6211\u5011\u60f3\u8981\u7372\u53d6\u6bcf\u500b\u570b\u5bb6\u7684\u7528\u6236\u6578\u91cf\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n
SELECT country, COUNT(*) FROM users GROUP BY country;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u6bcf\u500b\u570b\u5bb6\u53ca\u5176\u5c0d\u61c9\u7684\u7528\u6236\u6578\u91cf\uff0c\u4e26\u4e14\u6bcf\u500b\u570b\u5bb6\u53ea\u6703\u51fa\u73fe\u4e00\u6b21\u3002<\/p>\n
\u4f7f\u7528HAVING\u5b50\u53e5\u904e\u6ffe\u7d50\u679c<\/h2>\n
\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u6211\u5011\u53ef\u80fd\u9700\u8981\u5728\u4f7f\u7528GROUP BY<\/strong>\u5f8c\u9032\u4e00\u6b65\u904e\u6ffe\u7d50\u679c\u3002\u9019\u6642\u53ef\u4ee5\u4f7f\u7528HAVING<\/strong>\u5b50\u53e5\u3002<\/p>\n
SELECT country, COUNT(*) FROM users GROUP BY country HAVING COUNT(*) > 1;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u64c1\u6709\u591a\u65bc\u4e00\u500b\u7528\u6236\u7684\u570b\u5bb6\u3002<\/p>\n
\u4f7f\u7528UNION\u5408\u4f75\u67e5\u8a62\u7d50\u679c<\/h2>\n
\u5982\u679c\u9700\u8981\u5f9e\u591a\u500b\u8868\u4e2d\u7372\u53d6\u552f\u4e00\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528UNION<\/strong>\u64cd\u4f5c\u7b26\u3002\u9019\u500b\u64cd\u4f5c\u7b26\u53ef\u4ee5\u5408\u4f75\u591a\u500b\u67e5\u8a62\u7684\u7d50\u679c\uff0c\u4e26\u81ea\u52d5\u6392\u9664\u91cd\u8907\u7684\u884c\u3002<\/p>\n
SELECT column_name FROM table1 UNION SELECT column_name FROM table2;<\/code><\/pre>\n
\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u6709\u5169\u500b\u8868customers<\/strong>\u548cvendors<\/strong>\uff0c\u6211\u5011\u60f3\u8981\u7372\u53d6\u6240\u6709\u4e0d\u540c\u7684\u57ce\u5e02\uff1a<\/p>\n
SELECT city FROM customers UNION SELECT city FROM vendors;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56decustomers<\/strong>\u548cvendors<\/strong>\u8868\u4e2d\u6240\u6709\u552f\u4e00\u7684\u57ce\u5e02\u540d\u7a31\u3002<\/p>\n
\u7e3d\u7d50<\/h2>\n
\u5728MySQL\u4e2d\uff0c\u7372\u53d6\u552f\u4e00\u503c\u7684\u6280\u5de7\u6709\u5f88\u591a\uff0c\u4e3b\u8981\u5305\u62ec\u4f7f\u7528DISTINCT<\/strong>\u3001GROUP BY<\/strong>\u3001HAVING<\/strong>\u548cUNION<\/strong>\u7b49\u95dc\u9375\u5b57\u3002\u9019\u4e9b\u65b9\u6cd5\u4e0d\u50c5\u80fd\u5e6b\u52a9\u6211\u5011\u6709\u6548\u5730\u7ba1\u7406\u6578\u64da\uff0c\u9084\u80fd\u63d0\u9ad8\u67e5\u8a62\u7684\u6548\u7387\u3002<\/p>\n
\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\uff0c\u8003\u616e\u4f7f\u7528\u9999\u6e2fVPS<\/a>\u4f86\u904b\u884c\u60a8\u7684MySQL\u6578\u64da\u5eab\uff0c\u9019\u5c07\u70ba\u60a8\u7684\u696d\u52d9\u63d0\u4f9b\u7a69\u5b9a\u548c\u53ef\u9760\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u63a2\u7d22MySQL\u4e2d\u63d0\u53d6\u552f\u4e00\u503c\u7684\u6578\u64da\u5eab\u6aa2\u7d22\u6280\u5de7\uff0c\u63d0\u5347\u67e5\u8a62\u6548\u7387\uff0c\u512a\u5316\u6578\u64da\u7ba1\u7406\uff0c\u5be6\u73fe\u7cbe\u78ba\u6578\u64da\u5206\u6790\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-75670","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/75670","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=75670"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/75670\/revisions"}],"predecessor-version":[{"id":75671,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/75670\/revisions\/75671"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=75670"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=75670"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=75670"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}