{"id":200195,"date":"2025-05-06T09:30:14","date_gmt":"2025-05-06T01:30:14","guid":{"rendered":"https:\/\/server.hk\/cnblog\/200195\/"},"modified":"2025-05-06T09:30:14","modified_gmt":"2025-05-06T01:30:14","slug":"sql-%e6%9f%a5%e8%af%a2%e4%b8%ad%e7%9a%84%e5%86%85%e8%bf%9e%e6%8e%a5%e3%80%81%e5%b7%a6%e8%bf%9e%e6%8e%a5%e5%92%8c%e5%8f%b3%e8%bf%9e%e6%8e%a5%ef%bc%9a%e5%a6%82%e4%bd%95%e9%80%89%e6%8b%a9%e6%9c%80","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/200195\/","title":{"rendered":"SQL \u67e5\u8be2\u4e2d\u7684\u5185\u8fde\u63a5\u3001\u5de6\u8fde\u63a5\u548c\u53f3\u8fde\u63a5\uff1a\u5982\u4f55\u9009\u62e9\u6700\u5408\u9002\u7684\u8fde\u63a5\u65b9\u5f0f\uff1f"},"content":{"rendered":"<p><b><\/b> <\/p>\n<h1>SQL \u67e5\u8be2\u4e2d\u7684\u5185\u8fde\u63a5\u3001\u5de6\u8fde\u63a5\u548c\u53f3\u8fde\u63a5\uff1a\u5982\u4f55\u9009\u62e9\u6700\u5408\u9002\u7684\u8fde\u63a5\u65b9\u5f0f\uff1f<\/h1>\n<p>\u5728\u6570\u636e\u5e93\u5b9e\u6218\u5f00\u53d1\u7684\u8fc7\u7a0b\u4e2d\uff0c\u6211\u4eec\u7ecf\u5e38\u4f1a\u9047\u5230\u4e00\u4e9b\u8fd9\u6837\u90a3\u6837\u7684\u95ee\u9898\uff0c\u7136\u540e\u8981\u5361\u597d\u534a\u5929\uff0c\u7b49\u95ee\u9898\u89e3\u51b3\u4e86\u624d\u53d1\u73b0\u539f\u6765\u4e00\u4e9b\u7ec6\u8282\u77e5\u8bc6\u70b9\u8fd8\u662f\u6ca1\u6709\u638c\u63e1\u597d\u3002\u4eca\u5929\u4e3b\u673a\u5b9d\u8d1d\u5c31\u6574\u7406\u5206\u4eab\u300aSQL \u67e5\u8be2\u4e2d\u7684\u5185\u8fde\u63a5\u3001\u5de6\u8fde\u63a5\u548c\u53f3\u8fde\u63a5\uff1a\u5982\u4f55\u9009\u62e9\u6700\u5408\u9002\u7684\u8fde\u63a5\u65b9\u5f0f\uff1f\u300b\uff0c\u804a\u804a\uff0c\u5e0c\u671b\u53ef\u4ee5\u5e2e\u52a9\u5230\u6b63\u5728\u52aa\u529b\u8d5a\u94b1\u7684\u4f60\u3002<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.17golang.com\/uploads\/20241028\/1730074744671ed87876164.jpg\" class=\"aligncenter\"><\/p>\n<p><strong>\u5173\u4e8e\u5185\u8fde\u63a5\u3001\u5de6\u8fde\u63a5\u548c\u53f3\u8fde\u63a5<\/strong><\/p>\n<p>\u5728\u64b0\u5199\u67e5\u8be2 sql \u65f6\uff0c\u4e86\u89e3\u5185\u8fde\u63a5\u3001\u5de6\u8fde\u63a5\u548c\u53f3\u8fde\u63a5\u7684\u533a\u522b\u81f3\u5173\u91cd\u8981\u3002\u867d\u7136\u539f\u7406\u5bb9\u6613\u7406\u89e3\uff0c\u4f46\u5b9e\u9645\u5e94\u7528\u4e2d\u96be\u514d\u4ee4\u4eba\u8ff7\u60d1\u3002\u672c\u6587\u5c06\u5728\u6613\u4e8e\u7406\u89e3\u7684\u793a\u4f8b\u4e2d\uff0c\u5206\u4eab\u5b83\u4eec\u7684\u5e94\u7528\u573a\u666f\u3002<\/p>\n<p><strong>1. \u5185\u8fde\u63a5<\/strong><\/p>\n<p>\u5185\u8fde\u63a5\u7528\u4e8e\u53d6\u51fa\u4e24\u5f20\u8868\u4e2d\u5171\u6709\u6570\u636e\u7684\u8bb0\u5f55\u3002\u4ee5\u4e0b\u793a\u4f8b\u4e2d\uff0ca\uff08\u5de6\u8868\uff09\u548cb\uff08\u53f3\u8868\uff09\u4f7f\u7528\u5217 key \u8fdb\u884c\u5173\u8054\u3002<\/p>\n<pre>select * from a inner join b on a.key = b.key;<\/pre>\n<p><strong>2. \u5de6\u8fde\u63a5<\/strong><\/p>\n<p>\u5de6\u8fde\u63a5\u9664\u4e86\u8fd4\u56de\u5171\u6709\u7684\u8bb0\u5f55\u5916\uff0c\u8fd8\u4f1a\u8fd4\u56de\u53f3\u8868\u4e2d\u72ec\u6709\u4e14\u4e0e\u5de6\u8868\u5173\u8054\u4e0d\u4e0a\u7684\u6570\u636e\u3002<\/p>\n<pre>select * from a left join b on a.key = b.key;<\/pre>\n<p><strong>3. \u53f3\u8fde\u63a5<\/strong><\/p>\n<p>\u4e0e\u5de6\u8fde\u63a5\u7c7b\u4f3c\uff0c\u53f3\u8fde\u63a5\u9664\u4e86\u8fd4\u56de\u5171\u6709\u7684\u8bb0\u5f55\u5916\uff0c\u8fd8\u4f1a\u8fd4\u56de\u5de6\u8868\u4e2d\u72ec\u6709\u4e14\u4e0e\u53f3\u8868\u5173\u8054\u4e0d\u4e0a\u7684\u6570\u636e\u3002<\/p>\n<pre>SELECT * FROM A RIGHT JOIN B ON A.key = B.key;<\/pre>\n<p><strong>\u62d3\u5c55\u5e94\u7528\uff1a<\/strong><\/p>\n<ul>\n<li><strong>\u53ea\u53d6\u5de6\u8868\uff08a\uff09\u72ec\u6709\u6570\u636e\uff1a<\/strong>\u4f7f\u7528\u5de6\u8fde\u63a5\uff0c\u5e76\u4f7f\u7528 where b.key is null \u67e5\u8be2\u53f3\u8868\u4e2d key \u4e3a null \u7684\u8bb0\u5f55\u3002<\/li>\n<li><strong>\u53ea\u53d6\u53f3\u8868\uff08b\uff09\u72ec\u6709\u6570\u636e\uff1a<\/strong>\u4f7f\u7528\u5de6\u8fde\u63a5\uff0c\u5e76\u4f7f\u7528 where a.key is null \u67e5\u8be2\u5de6\u8868\u4e2d key \u4e3a null \u7684\u8bb0\u5f55\u3002<\/li>\n<li><strong>\u5168\u8fde\u63a5\uff1a<\/strong>mysql \u4e0d\u652f\u6301\u5168\u8fde\u63a5\uff0c\u4f46\u53ef\u4ee5\u4f7f\u7528 union \u5b9e\u73b0\u7c7b\u4f3c\u6548\u679c\uff0c\u8fd4\u56de\u5de6\u53f3\u4e24\u8868\u7684\u6240\u6709\u8bb0\u5f55\u3002<\/li>\n<li><strong>\u53d6\u51fa\u5de6\u53f3\u4e24\u8868\u5404\u81ea\u72ec\u6709\u6570\u636e\uff1a<\/strong>\u4f7f\u7528\u5168\u8fde\u63a5\uff0c\u518d\u4f7f\u7528 where a.key is null or b.key is null \u67e5\u8be2 key \u4e3a null \u7684\u8bb0\u5f55\u3002<\/li>\n<\/ul>\n<p>\u4ee5\u4e0a\u5c31\u662f\u300aSQL \u67e5\u8be2\u4e2d\u7684\u5185\u8fde\u63a5\u3001\u5de6\u8fde\u63a5\u548c\u53f3\u8fde\u63a5\uff1a\u5982\u4f55\u9009\u62e9\u6700\u5408\u9002\u7684\u8fde\u63a5\u65b9\u5f0f\uff1f\u300b\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u5173\u4e8e\u7684\u8d44\u6599\u8bf7\u5173\u6ce8\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\uff01<\/p>\n<dl>\n<dt>\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"<p>SQL \u67e5\u8be2\u4e2d\u7684\u5185\u8fde\u63a5\u3001\u5de6\u8fde\u63a5\u548c&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-200195","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200195","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"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=200195"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200195\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=200195"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=200195"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=200195"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}