{"id":76234,"date":"2024-10-16T04:58:16","date_gmt":"2024-10-15T20:58:16","guid":{"rendered":"https:\/\/server.hk\/cnblog\/76234\/"},"modified":"2024-10-16T04:58:17","modified_gmt":"2024-10-15T20:58:17","slug":"mysql%e5%85%a5%e9%96%80%ef%bc%9a%e4%bd%bf%e7%94%a8left-join%e9%97%9c%e9%8d%b5%e5%ad%97%e8%bf%94%e5%9b%9e%e5%b7%a6%e8%a1%a8%e4%b8%ad%e7%9a%84%e6%89%80%e6%9c%89%e8%a8%98%e9%8c%84%e5%92%8c%e5%8f%b3","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/76234\/","title":{"rendered":"MySQL\u5165\u9580\uff1a\u4f7f\u7528LEFT JOIN\u95dc\u9375\u5b57\u8fd4\u56de\u5de6\u8868\u4e2d\u7684\u6240\u6709\u8a18\u9304\u548c\u53f3\u8868\u4e2d\u5339\u914d\u7684\u8a18\u9304\u3002"},"content":{"rendered":"<h1 id=\"mysql%e5%85%a5%e9%96%80%ef%bc%9a%e4%bd%bf%e7%94%a8left-join%e9%97%9c%e9%8d%b5%e5%ad%97%e8%bf%94%e5%9b%9e%e5%b7%a6%e8%a1%a8%e4%b8%ad%e7%9a%84%e6%89%80%e6%9c%89%e8%a8%98%e9%8c%84%e5%92%8c%e5%8f%b3-IDXmJRLurc\">MySQL\u5165\u9580\uff1a\u4f7f\u7528LEFT JOIN\u95dc\u9375\u5b57\u8fd4\u56de\u5de6\u8868\u4e2d\u7684\u6240\u6709\u8a18\u9304\u548c\u53f3\u8868\u4e2d\u5339\u914d\u7684\u8a18\u9304<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0cMySQL\u662f\u4e00\u500b\u975e\u5e38\u6d41\u884c\u7684\u9078\u64c7\uff0c\u56e0\u70ba\u5b83\u7684\u9748\u6d3b\u6027\u548c\u5f37\u5927\u7684\u529f\u80fd\u3002\u7576\u6211\u5011\u9700\u8981\u5f9e\u591a\u500b\u8868\u4e2d\u63d0\u53d6\u6578\u64da\u6642\uff0cJOIN\u64cd\u4f5c\u662f\u4e0d\u53ef\u6216\u7f3a\u7684\u3002\u672c\u6587\u5c07\u91cd\u9ede\u4ecb\u7d39LEFT JOIN\u95dc\u9375\u5b57\uff0c\u4e26\u89e3\u91cb\u5982\u4f55\u4f7f\u7528\u5b83\u4f86\u8fd4\u56de\u5de6\u8868\u4e2d\u7684\u6240\u6709\u8a18\u9304\u4ee5\u53ca\u53f3\u8868\u4e2d\u5339\u914d\u7684\u8a18\u9304\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%afleft-join%ef%bc%9f-IDXmJRLurc\">\u4ec0\u9ebc\u662fLEFT JOIN\uff1f<\/h2>\n<p>LEFT JOIN\u662f\u4e00\u7a2e\u806f\u63a5\u64cd\u4f5c\uff0c\u4e3b\u8981\u7528\u65bc\u5f9e\u5169\u500b\u6216\u591a\u500b\u8868\u4e2d\u6aa2\u7d22\u6578\u64da\u3002\u5b83\u7684\u7279\u9ede\u662f\u8fd4\u56de\u5de6\u8868\u4e2d\u7684\u6240\u6709\u8a18\u9304\uff0c\u5373\u4f7f\u53f3\u8868\u4e2d\u6c92\u6709\u5339\u914d\u7684\u8a18\u9304\u3002\u5728\u9019\u7a2e\u60c5\u6cc1\u4e0b\uff0c\u53f3\u8868\u7684\u5b57\u6bb5\u5c07\u986f\u793a\u70baNULL\u3002<\/p>\n<h2 id=\"left-join%e7%9a%84%e8%aa%9e%e6%b3%95-IDXmJRLurc\">LEFT JOIN\u7684\u8a9e\u6cd5<\/h2>\n<p>LEFT JOIN\u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT \u5217\u540d1, \u5217\u540d2, ...\nFROM \u5de6\u8868\nLEFT JOIN \u53f3\u8868\nON \u5de6\u8868.\u5171\u540c\u5217 = \u53f3\u8868.\u5171\u540c\u5217;<\/code><\/pre>\n<p>\u5728\u9019\u88e1\uff0c&#8221;\u5de6\u8868&#8221;\u662f\u6211\u5011\u5e0c\u671b\u8fd4\u56de\u6240\u6709\u8a18\u9304\u7684\u8868\uff0c\u800c&#8221;\u53f3\u8868&#8221;\u662f\u6211\u5011\u5e0c\u671b\u5f9e\u4e2d\u7372\u53d6\u5339\u914d\u8a18\u9304\u7684\u8868\u3002&#8221;\u5171\u540c\u5217&#8221;\u662f\u5169\u500b\u8868\u4e2d\u7528\u65bc\u5339\u914d\u7684\u5217\u3002<\/p>\n<h2 id=\"%e5%af%a6%e9%9a%9b%e7%af%84%e4%be%8b-IDXmJRLurc\">\u5be6\u969b\u7bc4\u4f8b<\/h2>\n<p>\u5047\u8a2d\u6211\u5011\u6709\u5169\u500b\u8868\uff1a<strong>customers<\/strong>\uff08\u5ba2\u6236\uff09\u548c<strong>orders<\/strong>\uff08\u8a02\u55ae\uff09\u3002<\/p>\n<ul>\n<li><strong>customers<\/strong>\u8868\uff1a<\/li>\n<ul>\n<li>customer_id<\/li>\n<li>customer_name<\/li>\n<\/ul>\n<li><strong>orders<\/strong>\u8868\uff1a<\/li>\n<ul>\n<li>order_id<\/li>\n<li>customer_id<\/li>\n<li>order_date<\/li>\n<\/ul>\n<\/ul>\n<p>\u6211\u5011\u5e0c\u671b\u67e5\u8a62\u6240\u6709\u5ba2\u6236\u53ca\u5176\u8a02\u55ae\u3002\u5982\u679c\u67d0\u4e9b\u5ba2\u6236\u6c92\u6709\u8a02\u55ae\uff0c\u6211\u5011\u4ecd\u7136\u5e0c\u671b\u986f\u793a\u9019\u4e9b\u5ba2\u6236\u7684\u4fe1\u606f\u3002\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0bSQL\u67e5\u8a62\uff1a<\/p>\n<pre><code>SELECT customers.customer_id, customers.customer_name, orders.order_id, orders.order_date\nFROM customers\nLEFT JOIN orders\nON customers.customer_id = orders.customer_id;<\/code><\/pre>\n<p>\u5728\u9019\u500b\u67e5\u8a62\u4e2d\uff0c\u6211\u5011\u5f9e<strong>customers<\/strong>\u8868\u4e2d\u9078\u64c7\u6240\u6709\u5ba2\u6236\u7684ID\u548c\u540d\u7a31\uff0c\u4e26\u5f9e<strong>orders<\/strong>\u8868\u4e2d\u9078\u64c7\u8a02\u55aeID\u548c\u8a02\u55ae\u65e5\u671f\u3002\u5373\u4f7f\u67d0\u4e9b\u5ba2\u6236\u6c92\u6709\u8a02\u55ae\uff0c\u67e5\u8a62\u4ecd\u7136\u6703\u8fd4\u56de\u9019\u4e9b\u5ba2\u6236\u7684\u8a18\u9304\uff0c\u4e26\u4e14\u8a02\u55aeID\u548c\u8a02\u55ae\u65e5\u671f\u5c07\u986f\u793a\u70baNULL\u3002<\/p>\n<h2 id=\"left-join%e7%9a%84%e6%87%89%e7%94%a8%e5%a0%b4%e6%99%af-IDXmJRLurc\">LEFT JOIN\u7684\u61c9\u7528\u5834\u666f<\/h2>\n<p>LEFT JOIN\u5728\u8a31\u591a\u5834\u666f\u4e2d\u90fd\u975e\u5e38\u6709\u7528\uff0c\u4f8b\u5982\uff1a<\/p>\n<ul>\n<li>\u67e5\u8a62\u6240\u6709\u7528\u6236\u53ca\u5176\u6700\u8fd1\u7684\u6d3b\u52d5\uff0c\u5373\u4f7f\u67d0\u4e9b\u7528\u6236\u6c92\u6709\u6d3b\u52d5\u8a18\u9304\u3002<\/li>\n<li>\u7372\u53d6\u6240\u6709\u7522\u54c1\u53ca\u5176\u92b7\u552e\u8a18\u9304\uff0c\u5373\u4f7f\u67d0\u4e9b\u7522\u54c1\u5c1a\u672a\u552e\u51fa\u3002<\/li>\n<li>\u986f\u793a\u6240\u6709\u54e1\u5de5\u53ca\u5176\u9805\u76ee\uff0c\u5373\u4f7f\u67d0\u4e9b\u54e1\u5de5\u672a\u53c3\u8207\u4efb\u4f55\u9805\u76ee\u3002<\/li>\n<\/ul>\n<h2 id=\"%e6%b3%a8%e6%84%8f%e4%ba%8b%e9%a0%85-IDXmJRLurc\">\u6ce8\u610f\u4e8b\u9805<\/h2>\n<p>\u5728\u4f7f\u7528LEFT JOIN\u6642\uff0c\u61c9\u6ce8\u610f\u4ee5\u4e0b\u5e7e\u9ede\uff1a<\/p>\n<ul>\n<li>LEFT JOIN\u53ef\u80fd\u6703\u5c0e\u81f4\u8fd4\u56de\u5927\u91cf\u6578\u64da\uff0c\u7279\u5225\u662f\u7576\u5de6\u8868\u7684\u8a18\u9304\u6578\u91cf\u5f88\u5927\u6642\u3002<\/li>\n<li>\u5728\u9032\u884c\u591a\u500bJOIN\u64cd\u4f5c\u6642\uff0c\u61c9\u8b39\u614e\u8a2d\u8a08\u67e5\u8a62\uff0c\u4ee5\u907f\u514d\u6027\u80fd\u554f\u984c\u3002<\/li>\n<li>\u78ba\u4fdd\u5171\u540c\u5217\u7684\u6578\u64da\u985e\u578b\u76f8\u540c\uff0c\u4ee5\u907f\u514d\u4e0d\u5fc5\u8981\u7684\u932f\u8aa4\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b8%bd%e7%b5%90-IDXmJRLurc\">\u7e3d\u7d50<\/h2>\n<p>LEFT JOIN\u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u53ef\u4ee5\u5e6b\u52a9\u6211\u5011\u5f9e\u591a\u500b\u8868\u4e2d\u63d0\u53d6\u6240\u9700\u7684\u6578\u64da\u3002\u901a\u904e\u4f7f\u7528LEFT JOIN\uff0c\u6211\u5011\u53ef\u4ee5\u78ba\u4fdd\u5373\u4f7f\u5728\u53f3\u8868\u4e2d\u6c92\u6709\u5339\u914d\u7684\u8a18\u9304\u6642\uff0c\u5de6\u8868\u4e2d\u7684\u6240\u6709\u8a18\u9304\u4ecd\u7136\u6703\u88ab\u8fd4\u56de\u3002\u9019\u5728\u6578\u64da\u5206\u6790\u548c\u5831\u544a\u4e2d\u975e\u5e38\u6709\u7528\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\uff0c\u8003\u616e\u4f7f\u7528<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u4f86\u6258\u7ba1\u60a8\u7684MySQL\u6578\u64da\u5eab\uff0c\u9019\u5c07\u70ba\u60a8\u7684\u61c9\u7528\u7a0b\u5e8f\u63d0\u4f9b\u7a69\u5b9a\u548c\u53ef\u9760\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5b78\u7fd2MySQL\u5165\u9580\uff0c\u638c\u63e1\u4f7f\u7528LEFT JOIN\u95dc\u9375\u5b57\uff0c\u8fd4\u56de\u5de6\u8868\u4e2d\u7684\u6240\u6709\u8a18\u9304\u53ca\u53f3\u8868\u4e2d\u5339\u914d\u7684\u8a18\u9304\uff0c\u63d0\u5347\u6578\u64da\u67e5\u8a62\u6280\u5de7\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-76234","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/76234","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=76234"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/76234\/revisions"}],"predecessor-version":[{"id":76235,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/76234\/revisions\/76235"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=76234"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=76234"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=76234"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}