{"id":205237,"date":"2025-05-29T11:40:59","date_gmt":"2025-05-29T03:40:59","guid":{"rendered":"https:\/\/server.hk\/cnblog\/205237\/"},"modified":"2025-05-29T11:40:59","modified_gmt":"2025-05-29T03:40:59","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%ad%97%e6%ae%b5%e7%9a%84%e6%9c%80%e5%a4%a7%e5%80%bc","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/205237\/","title":{"rendered":"\u5982\u4f55\u4f7f\u7528 MySQL LEFT JOIN \u66f4\u65b0\u8868\u4e2d\u5b57\u6bb5\u7684\u6700\u5927\u503c?"},"content":{"rendered":"<p><b><\/b>     <\/p>\n<h1>\u5982\u4f55\u4f7f\u7528 MySQL LEFT JOIN \u66f4\u65b0\u8868\u4e2d\u5b57\u6bb5\u7684\u6700\u5927\u503c? <\/h1>\n<p>\u54c8\u55bd\uff01\u5927\u5bb6\u597d\uff0c\u5f88\u9ad8\u5174\u53c8\u89c1\u9762\u4e86\uff0c\u6211\u662f\u7684\u4e00\u540d\u4f5c\u8005\uff0c\u4eca\u5929\u7531\u6211\u7ed9\u5927\u5bb6\u5e26\u6765\u4e00\u7bc7\uff0c\u672c\u6587\u4e3b\u8981\u4f1a\u8bb2\u5230<span style=\"color: #FF6600;, Helvetica, Arial, sans-serif;font-size: 14px;background-color: #FFFFFF\"><\/span>\u7b49\u7b49\u77e5\u8bc6\u70b9\uff0c\u5e0c\u671b\u5927\u5bb6\u4e00\u8d77\u5b66\u4e60\u8fdb\u6b65\uff0c\u4e5f\u6b22\u8fce\u5927\u5bb6\u5173\u6ce8\u3001\u70b9\u8d5e\u3001\u6536\u85cf\u3001\u8f6c\u53d1! \u4e0b\u9762\u5c31\u4e00\u8d77\u6765\u770b\u770b\u5427\uff01<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.17golang.com\/uploads\/20241126\/17326287426745d10602d52.jpg\" class=\"aligncenter\"><\/p>\n<p><strong>mysql \u7684 left join \u5982\u4f55\u7528\u4e8e\u66f4\u65b0\u8868\u4e2d\u5b57\u6bb5\u7684\u6700\u5927\u503c<\/strong><\/p>\n<p>\u60f3\u8981\u66f4\u65b0 student \u8868\u7684 score \u5b57\u6bb5\u4e3a score \u8868\u4e2d\u5bf9\u5e94\u5b66\u751f id \u6700\u5927\u7684\u4e00\u6761\u8bb0\u5f55\uff0c\u53ef\u4ee5\u4f7f\u7528 left join \u67e5\u8be2\u3002<\/p>\n<pre>update student\nset score = (\n  select max(score)\n  from score\n  where score.student_id = student.id\n)<\/pre>\n<p>\u5728\u8fd9\u4e2a\u67e5\u8be2\u4e2d\uff1a<\/p>\n<ul>\n<li>left join \u5c06 student \u548c score \u8868\u6309\u7167 student_id \u5b57\u6bb5\u8fde\u63a5\u3002<\/li>\n<li>\u5185\u90e8\u5b50\u67e5\u8be2 select max(score) \u627e\u51fa\u6bcf\u4e2a\u5b66\u751f score \u8868\u4e2d\u6700\u5927\u7684\u5206\u6570\u3002<\/li>\n<li>\u5916\u90e8\u67e5\u8be2\u5c06\u5185\u90e8\u67e5\u8be2\u7684\u7ed3\u679c\u66f4\u65b0\u5230 student \u8868\u4e2d\u76f8\u5e94\u7684 score \u5b57\u6bb5\u3002<\/li>\n<\/ul>\n<p>\u5230\u8fd9\u91cc\uff0c\u6211\u4eec\u4e5f\u5c31\u8bb2\u5b8c\u4e86\u300a\u5982\u4f55\u4f7f\u7528 MySQL LEFT JOIN \u66f4\u65b0\u8868\u4e2d\u5b57\u6bb5\u7684\u6700\u5927\u503c? \u300b\u7684\u5185\u5bb9\u4e86\u3002\u4e2a\u4eba\u8ba4\u4e3a\uff0c\u57fa\u7840\u77e5\u8bc6\u7684\u5b66\u4e60\u548c\u5de9\u56fa\uff0c\u662f\u4e3a\u4e86\u66f4\u597d\u7684\u5c06\u5176\u8fd0\u7528\u5230\u9879\u76ee\u4e2d\uff0c\u6b22\u8fce\u5173\u6ce8\u516c\u4f17\u53f7\uff0c\u5e26\u4f60\u4e86\u89e3\u66f4\u591a\u5173\u4e8e\u7684\u77e5\u8bc6\u70b9\uff01<\/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-205237","post","type-post","status-publish","format-standard","hentry","category-4925"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/205237","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=205237"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/205237\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=205237"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=205237"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=205237"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}