{"id":25886,"date":"2024-11-24T14:06:05","date_gmt":"2024-11-24T06:06:05","guid":{"rendered":"https:\/\/fwq.ai\/blog\/25886\/"},"modified":"2024-11-24T14:06:05","modified_gmt":"2024-11-24T06:06:05","slug":"%e5%a6%82%e4%bd%95%e4%bd%bf%e7%94%a8mysql-left-join-%e6%9b%b4%e6%96%b0%e5%ad%a6%e7%94%9f%e8%a1%a8%e4%b8%ad%e6%88%90%e7%bb%a9%e5%ad%97%e6%ae%b5%e4%b8%ba%e5%af%b9%e5%ba%94%e5%ad%a6%e7%94%9f%e5%9c%a8-2","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/25886\/","title":{"rendered":"\u5982\u4f55\u4f7f\u7528MySQL left join \u66f4\u65b0\u5b66\u751f\u8868\u4e2d\u6210\u7ee9\u5b57\u6bb5\u4e3a\u5bf9\u5e94\u5b66\u751f\u5728\u6210\u7ee9\u8868\u4e2d\u7684\u6700\u9ad8\u5206\uff1f"},"content":{"rendered":"

\"\u5982\u4f55\u4f7f\u7528MySQL<\/p>\n

left join \u5b9e\u73b0\u591a\u6761\u6570\u636e\u4e2d\u67d0\u5b57\u6bb5\u6700\u5927\u503c\u7684\u66f4\u65b0<\/strong><\/p>\n

\u5728mysql\u4e2d\uff0c\u5bf9\u4e8e\u66f4\u65b0student\u8868\u4e2dscore\u5b57\u6bb5\u7684\u503c\uff0c\u4f7f\u5176\u7b49\u4e8escore\u8868\u4e2d\u5bf9\u5e94student_id\u7684\u6700\u5927\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u65b9\u6cd5\uff1a<\/p>\n

\u67e5\u8be2\u8bed\u53e5\uff1a<\/strong><\/p>\n

update student set score=(select max(score) from score where score.student_id=student.id)<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u89e3\u91ca\uff1a<\/strong><\/p>\n
    \n
  •  left join:<\/strong> \u5c06student\u8868\u548cscore\u8868\u4ee5student_id\u5217\u8fdb\u884c\u8fde\u63a5\uff0c\u5bf9\u4e8estudent\u8868\u4e2d\u7684\u6bcf\u4e00\u884c\uff0c\u627e\u51fascore\u8868\u4e2d\u5bf9\u5e94\u7684\u6700\u5927score\u503c\u3002<\/li>\n
  •  max(score):<\/strong> \u83b7\u53d6\u5f97\u5206\u8868\u4e2d\u7279\u5b9a\u5b66\u751f\u5f97\u5206\u7684\u6700\u5927\u503c\u3002<\/li>\n
  •  where score.student_id=student.id:<\/strong> \u786e\u4fddscore\u8868\u7684student_id\u4e0estudent\u8868\u7684student_id\u5339\u914d\u3002<\/li>\n
  •  update student set score=():<\/strong> \u5c06student\u8868\u7684score\u5b57\u6bb5\u66f4\u65b0\u4e3a\u4ece( )\u4e2d\u9009\u51fa\u7684\u6700\u5927\u503c\u3002<\/li>\n<\/ul>\n
    \u6267\u884c\u6b64\u67e5\u8be2\u540e\uff0cstudent\u8868\u4e2d\u6bcf\u4e2a\u5b66\u751f\u7684score\u5b57\u6bb5\u5c06\u66f4\u65b0\u4e3a\u4ed6\u4eec\u5728score\u8868\u4e2d\u83b7\u5f97\u7684\u6700\u9ad8\u5206\u6570\u3002<\/p>\n
    \u4ee5\u4e0a\u5c31\u662f\u5982\u4f55\u4f7f\u7528MySQL left join \u66f4\u65b0\u5b66\u751f\u8868\u4e2d\u6210\u7ee9\u5b57\u6bb5\u4e3a\u5bf9\u5e94\u5b66\u751f\u5728\u6210\u7ee9\u8868\u4e2d\u7684\u6700\u9ad8\u5206\uff1f\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
    left join \u5b9e\u73b0\u591a\u6761\u6570\u636e\u4e2d\u67d0\u5b57\u6bb5\u6700\u5927\u503c\u7684\u66f4\u65b0 \u5728mysql\u4e2d\uff0c\u5bf9\u4e8e\u66f4\u65b0student\u8868\u4e2dscore\u5b57\u6bb5\u7684\u503c\uff0c\u4f7f\u5176\u7b49\u4e8escore\u8868\u4e2d\u5bf9\u5e94student_id\u7684\u6700\u5927\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u65b9\u6cd5\uff1a \u67e5\u8be2\u8bed\u53e5\uff1a update student set score=(select max(score) from score where score.student_id=student.id) \u767b\u5f55\u540e\u590d\u5236 \u89e3\u91ca\uff1a left join: \u5c06student\u8868\u548cscore\u8868\u4ee5student_id\u5217\u8fdb\u884c\u8fde\u63a5\uff0c\u5bf9\u4e8estudent\u8868\u4e2d\u7684\u6bcf\u4e00\u884c\uff0c\u627e\u51fascore\u8868\u4e2d\u5bf9\u5e94\u7684\u6700\u5927score\u503c\u3002 max(score): \u83b7\u53d6\u5f97\u5206\u8868\u4e2d\u7279\u5b9a\u5b66\u751f\u5f97\u5206\u7684\u6700\u5927\u503c\u3002 where score.student_id=student.id: \u786e\u4fddscore\u8868\u7684student_id\u4e0estudent\u8868\u7684student_id\u5339\u914d\u3002 update student set score=(): \u5c06student\u8868\u7684score\u5b57\u6bb5\u66f4\u65b0\u4e3a\u4ece( )\u4e2d\u9009\u51fa\u7684\u6700\u5927\u503c\u3002 \u6267\u884c\u6b64\u67e5\u8be2\u540e\uff0cstudent\u8868\u4e2d\u6bcf\u4e2a\u5b66\u751f\u7684score\u5b57\u6bb5\u5c06\u66f4\u65b0\u4e3a\u4ed6\u4eec\u5728score\u8868\u4e2d\u83b7\u5f97\u7684\u6700\u9ad8\u5206\u6570\u3002 \u4ee5\u4e0a\u5c31\u662f\u5982\u4f55\u4f7f\u7528MySQL left join \u66f4\u65b0\u5b66\u751f\u8868\u4e2d\u6210\u7ee9\u5b57\u6bb5\u4e3a\u5bf9\u5e94\u5b66\u751f\u5728\u6210\u7ee9\u8868\u4e2d\u7684\u6700\u9ad8\u5206\uff1f\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-25886","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/25886","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=25886"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/25886\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=25886"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=25886"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=25886"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}