{"id":158505,"date":"2020-09-08T14:33:43","date_gmt":"2020-09-08T06:33:43","guid":{"rendered":"http:\/\/4563.org\/?p=158505"},"modified":"2020-09-08T14:33:43","modified_gmt":"2020-09-08T06:33:43","slug":"mysql-leftjoin-%ef%bc%8c%e4%b8%80%e5%af%b9%e5%a4%9a%ef%bc%8c%e5%a6%82%e4%bd%95%e5%85%b3%e8%81%94%e5%88%b0%e5%8f%b3%e8%a1%a8%e6%9c%80%e6%96%b0%e7%9a%84%e8%ae%b0%e5%bd%95","status":"publish","type":"post","link":"http:\/\/4563.org\/?p=158505","title":{"rendered":"mysql leftjoin \uff0c\u4e00\u5bf9\u591a\uff0c\u5982\u4f55\u5173\u8054\u5230\u53f3\u8868\u6700\u65b0\u7684\u8bb0\u5f55"},"content":{"rendered":"
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mysql leftjoin \uff0c\u4e00\u5bf9\u591a\uff0c\u5982\u4f55\u5173\u8054\u5230\u53f3\u8868\u6700\u65b0\u7684\u8bb0\u5f55 <\/h1>\n

<\/p>\n

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\u8cc7\u6df1\u5927\u4f6c : wq67200976 <\/span> <\/i> 4<\/span> <\/div>\n
<\/div>\n<\/p><\/div>\n<\/p><\/div>\n<\/p><\/div>\n
\u5047\u8bbe\u6709\u6570\u636e\u8868 user, user_login,
user \u8868\uff0c
id | uid
1 | 1001
2 |002 <\/p>\n

user_login \u8868<\/p>\n

id | uid | content <\/p>\n

1 | 1001 | \u6570\u636e 1 |
2 | 1002 | \u6570\u636e 2 |
3 | 1001 | \u6570\u636e 3|
4 | 1001 | \u6570\u636e 4 |
5 | 1002 | \u6570\u636e 5| <\/p>\n

\u73b0\u5728\u5c06 user \u8868\u5f53\u4e3b\u8868\uff0c\u5de6\u8fde\u63a5\u67e5\u8be2 login \u8868\uff0c
select * from user as t1 left join (select max(id),content group by uid)
\u8fd9\u6837\u67e5\u5230\u7684\u7ed3\u679c uid \u548c content \u5bf9\u4e0d\u4e0a\uff0c\u4e5f\u5c31\u662f\u4f1a\u968f\u673a\u9009\u62e9\u4e00\u4e2a\u503c\uff0c<\/p>\n

\u50cf\u8fd9\u79cd\u60c5\u51b5\u60f3\u8981\u6839\u636e\u4e3b\u8868\u7684 uid\uff0c\u4e0d\u540c\u7684 uid \u5339\u914d\u5173\u8054\u8868\u4e2d uid \u76f8\u7b49\u7684\u6700\u65b0\u4e00\u6761\u8bb0\u5f55\u8be5\u5982\u4f55\u505a\u3002<\/p>\n

\u8fd9\u4e2a\u8868\u5b57\u6bb5\u7b49\u90fd\u662f\u968f\u624b\u5199\u7684\uff0c\u4e0d\u7528\u8003\u8651\u592a\u591a\uff0c\u50cf\u8fd9\u79cd\u80fd\u4e0d\u80fd\u901a\u8fc7\u53ea\u901a\u8fc7 sql \u8bed\u53e5\u67e5\u51fa\u6765 <\/p><\/div>\n

\u5927\u4f6c\u6709\u8a71\u8aaa<\/b> (2<\/span>) <\/div>\n
<\/div>\n<\/p><\/div>\n<\/p><\/div>\n
    \n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : yeqizhang <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u53f3\u8868\u5efa\u8bae\u518d\u5305\u88c5\u4e00\u5c42\u67e5 maxID \u8bb0\u5f55\u7684 content \u3002<\/p>\n

    \u4e0d\u77e5\u9053\u6211\u5370\u8c61\u4e2d\u6709\u95ee\u9898\u8fd8\u662f\u65b0\u7684\u7279\u6027\u5565\u7684\uff0c\u6211\u4e4b\u524d\u7528 group by\uff0c\u7ed3\u679c\u4e2d\u53ea\u80fd\u662f group by \u540e\u7684\u5b57\u6bb5\u52a0\u805a\u5408\u51fd\u6570\u4e4b\u7c7b\u7684 <\/p><\/div>\n<\/p><\/div>\n<\/li>\n

  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : nuistzhou <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u53ef\u4ee5\u5148\u7528 group by \u5904\u7406 login \u8868\u62ff\u5230\u6bcf\u4e2a uid \u7684\u6700\u65b0 id \u7684 record\uff0c\u7136\u540e\u63d2\u56de user \u8868\u5427\uff0c\u5e94\u8be5\u5c31\u6ca1\u6709\u591a\u5bf9\u4e00\u63d2\u5165\u8fd9\u79cd\u968f\u673a\u95ee\u9898\u6027\u4e86\u3002 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n","protected":false},"excerpt":{"rendered":"

    mysql leftjoin \uff0c\u4e00…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[],"tags":[],"_links":{"self":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/158505"}],"collection":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=158505"}],"version-history":[{"count":0,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/158505\/revisions"}],"wp:attachment":[{"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=158505"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=158505"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=158505"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}