{"id":204803,"date":"2025-05-29T15:04:18","date_gmt":"2025-05-29T07:04:18","guid":{"rendered":"https:\/\/server.hk\/cnblog\/204803\/"},"modified":"2025-05-29T15:04:18","modified_gmt":"2025-05-29T07:04:18","slug":"%e5%a6%82%e4%bd%95%e4%bd%bf%e7%94%a8-mysql-left-join-%e6%9b%b4%e6%96%b0%e8%a1%a8%e4%b8%ad%e5%a4%9a%e4%b8%aa%e8%ae%b0%e5%bd%95%e7%9a%84%e6%9c%80%e5%a4%a7%e5%80%bc%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/204803\/","title":{"rendered":"\u5982\u4f55\u4f7f\u7528 MySQL left join \u66f4\u65b0\u8868\u4e2d\u591a\u4e2a\u8bb0\u5f55\u7684\u6700\u5927\u503c\uff1f"},"content":{"rendered":"<p><b><\/b>     <\/p>\n<h1>\u5982\u4f55\u4f7f\u7528 MySQL left join \u66f4\u65b0\u8868\u4e2d\u591a\u4e2a\u8bb0\u5f55\u7684\u6700\u5927\u503c\uff1f<\/h1>\n<p>\u600e\u4e48\u5165\u95e8\u6587\u7ae0\u7f16\u7a0b\uff1f\u9700\u8981\u5b66\u4e60\u54ea\u4e9b\u77e5\u8bc6\u70b9\uff1f\u8fd9\u662f\u65b0\u624b\u4eec\u521a\u63a5\u89e6\u7f16\u7a0b\u65f6\u5e38\u89c1\u7684\u95ee\u9898\uff1b\u4e0b\u9762\u5c31\u6765\u7ed9\u5927\u5bb6\u6574\u7406\u5206\u4eab\u4e00\u4e9b\u77e5\u8bc6\u70b9\uff0c\u5e0c\u671b\u80fd\u591f\u7ed9\u521d\u5b66\u8005\u4e00\u4e9b\u5e2e\u52a9\u3002\u672c\u7bc7\u6587\u7ae0\u5c31\u6765\u4ecb\u7ecd\u300a\u5982\u4f55\u4f7f\u7528 MySQL left join \u66f4\u65b0\u8868\u4e2d\u591a\u4e2a\u8bb0\u5f55\u7684\u6700\u5927\u503c\uff1f\u300b\uff0c\u6d89\u53ca\u5230\uff0c\u6709\u9700\u8981\u7684\u53ef\u4ee5\u6536\u85cf\u4e00\u4e0b<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.17golang.com\/uploads\/20241116\/17317578996738874be7d43.jpg\" class=\"aligncenter\"><\/p>\n<p><strong>mysql left join \u66f4\u65b0\u8868\u4e2d\u591a\u4e2a\u8bb0\u5f55\u7684\u6700\u5927\u503c<\/strong><\/p>\n<p>\u60f3\u8981\u5c06 student \u8868\u7684 score \u5b57\u6bb5\u66f4\u65b0\u4e3a score \u8868\u4e2d\u540c\u4e2a student_id \u4e0b\u7684\u6700\u5927\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528 left join \u8bed\u53e5\u3002<\/p>\n<p>\u793a\u4f8b\uff1a<\/p>\n<p><strong>student \u8868<\/strong><\/p>\n<table>\n<thead>\n<tr>\n<th>id<\/th>\n<th>name<\/th>\n<th>score<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>1<\/td>\n<td>\u5c0f\u660e<\/td>\n<td>null<\/td>\n<\/tr>\n<tr>\n<td>2<\/td>\n<td>\u5c0f\u7ea2<\/td>\n<td>null<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><strong>score \u8868<\/strong><\/p>\n<table>\n<thead>\n<tr>\n<th>id<\/th>\n<th>student_id<\/th>\n<th>score<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>1<\/td>\n<td>1<\/td>\n<td>80<\/td>\n<\/tr>\n<tr>\n<td>2<\/td>\n<td>2<\/td>\n<td>88<\/td>\n<\/tr>\n<tr>\n<td>3<\/td>\n<td>1<\/td>\n<td>78<\/td>\n<\/tr>\n<tr>\n<td>4<\/td>\n<td>2<\/td>\n<td>98<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><strong>\u66f4\u65b0\u67e5\u8be2<\/strong><\/p>\n<pre>update student set score = (\n  select max(score)\n  from score\n  where score.student_id = student.id\n)<\/pre>\n<p><strong>\u6267\u884c\u6b64\u67e5\u8be2\u540e\uff0cstudent \u8868\u5c06\u66f4\u65b0\u4e3a\uff1a<\/strong><\/p>\n<table>\n<thead>\n<tr>\n<th>id<\/th>\n<th>name<\/th>\n<th>score<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>1<\/td>\n<td>\u5c0f\u660e<\/td>\n<td>80<\/td>\n<\/tr>\n<tr>\n<td>2<\/td>\n<td>\u5c0f\u7ea2<\/td>\n<td>98<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u6587\u4e2d\u5173\u4e8e\u7684\u77e5\u8bc6\u4ecb\u7ecd\uff0c\u5e0c\u671b\u5bf9\u4f60\u7684\u5b66\u4e60\u6709\u6240\u5e2e\u52a9\uff01\u82e5\u662f\u53d7\u76ca\u532a\u6d45\uff0c\u90a3\u5c31\u52a8\u52a8\u9f20\u6807\u6536\u85cf\u8fd9\u7bc7\u300a\u5982\u4f55\u4f7f\u7528 MySQL left join \u66f4\u65b0\u8868\u4e2d\u591a\u4e2a\u8bb0\u5f55\u7684\u6700\u5927\u503c\uff1f\u300b\u6587\u7ae0\u5427\uff0c\u4e5f\u53ef\u5173\u6ce8\u516c\u4f17\u53f7\u4e86\u89e3\u76f8\u5173\u6280\u672f\u6587\u7ae0\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5982\u4f55\u4f7f\u7528 MySQL left &#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":[4925],"tags":[],"class_list":["post-204803","post","type-post","status-publish","format-standard","hentry","category-4925"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/204803","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=204803"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/204803\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=204803"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=204803"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=204803"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}