{"id":271830,"date":"2021-01-11T08:38:32","date_gmt":"2021-01-11T00:38:32","guid":{"rendered":"http:\/\/4563.org\/?p=271830"},"modified":"2021-01-11T08:38:32","modified_gmt":"2021-01-11T00:38:32","slug":"mongo-%e8%81%9a%e5%90%88%e6%97%b6%e7%9a%84max-%e6%93%8d%e4%bd%9c%e4%b8%ba%e4%bb%80%e4%b9%88%e6%b2%a1%e6%9c%89%e8%b5%b0%e7%b4%a2%e5%bc%95%ef%bc%9f","status":"publish","type":"post","link":"http:\/\/4563.org\/?p=271830","title":{"rendered":"Mongo \u805a\u5408\u65f6\u7684$max \u64cd\u4f5c\u4e3a\u4ec0\u4e48\u6ca1\u6709\u8d70\u7d22\u5f15\uff1f"},"content":{"rendered":"
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Mongo \u805a\u5408\u65f6\u7684$max \u64cd\u4f5c\u4e3a\u4ec0\u4e48\u6ca1\u6709\u8d70\u7d22\u5f15\uff1f <\/h1>\n

<\/p>\n

\n
\u8cc7\u6df1\u5927\u4f6c : diyazhu <\/span> <\/i> 0<\/span> <\/div>\n
<\/div>\n<\/p><\/div>\n<\/p><\/div>\n<\/p><\/div>\n
\u4eca\u5929\u5728\u7ebf\u4e0a\u9047\u5230\u7684\u95ee\u9898\u9047\u5230\u4e00\u4e2a\u6162\u67e5\u8be2\u7684\u95ee\u9898\uff1a
\u60f3\u8981\u627e\u5230\u8868 A \u7684\u67d0\u4e2a\u5b57\u6bb5\u7684\u6700\u5927\u503c\uff0c\u6bd4\u5982\u8bf4 date \u5b57\u6bb5\u3002\u539f\u5148\u5199\u7684\u67e5\u8be2\u8bed\u53e5\u5982\u4e0b\uff1a<\/p>\n

db.A.aggregate({$group:{_id:null, max_date:{$max:”$date”}}})<\/p>\n

\u8fd9\u5728\u53ea\u6709\u5341\u4e07\u6570\u636e\u91cf\u7ea7\u7684\u65f6\u5019\u8fd4\u56de\u975e\u5e38\u5feb\uff0c\u53ef\u662f\u76ee\u524d\u5df2\u7ecf\u6709\u767e\u4e07\u91cf\u7ea7\u7684\uff0c\u7ebf\u4e0a\u67e5\u8be2\u5c31\u53d8\u5f97\u5f88\u6162\u3002
explain \u540e\u53d1\u73b0\u5c45\u7136\u662f\u5168\u8868\u626b\u63cf\u3002<\/p>\n

\u7d22\u5f15\u662f\u80af\u5b9a\u5efa\u4e86\u7684\u3002\u4f46\u5efa\u7684\u662f\u590d\u5408\u7d22\u5f15\uff0cdate \u5b57\u6bb5\u662f\u6700\u5de6\u8fb9\u7684\u5b57\u6bb5\u3002<\/p>\n

\u8bf7\u6559\u5404\u4f4d\u5927\u4f6c\uff0c\u4e0a\u9762\u8fd9\u4e2a\u67e5\u8be2\u4e3a\u4ec0\u4e48\u6ca1\u6709\u8d70\u7d22\u5f15\u5462\uff1f<\/p>\n

\u6362\u4e00\u79cd\u5199\u6cd5\uff0c<\/p>\n

db.A.find().sort({date:-1}).limit(1)<\/p>\n

\u53d1\u73b0\u5c31\u8d70\u4e86\u7d22\u5f15\u3002\u5f88\u5947\u602a\uff01 <\/p><\/div>\n

\u5927\u4f6c\u6709\u8a71\u8aaa<\/b> (3<\/span>) <\/div>\n
<\/div>\n<\/p><\/div>\n<\/p><\/div>\n
    \n
  • \n
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    \u8cc7\u6df1\u5927\u4f6c : snachx <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u4f60\u8fd9\u79cd\u60c5\u51b5\u5c31\u662f\u4e0d\u4f1a\u7528\u7d22\u5f15\u7684\uff0c$group \u5728\u7279\u5b9a\u6761\u4ef6\u4e0b\u624d\u4f1a\u7528\u7d22\u5f15<\/p>\n

    https:\/\/docs.mongodb.com\/master\/core\/aggregation-pipeline\/#pipeline-operators-and-indexes <\/p><\/div>\n<\/p><\/div>\n<\/li>\n

  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : JCZ2MkKb5S8ZX9pq <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u611f\u89c9 id null \u90a3\u6b65\u7c7b\u4f3c\u505a\u4e86\u4e00\u6b21\u6620\u5c04\uff0c\u6620\u5c04\u7684\u7ed3\u679c\u5df2\u7ecf\u6ca1\u6709 index \u4e86\u3002 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u4e3b<\/span> \u8cc7\u6df1\u5927\u4f6c : diyazhu <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    @snachx @JCZ2MkKb5S8ZX9pq \u611f\u8c22\u5927\u4f6c\u7684\u56de\u590d <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n","protected":false},"excerpt":{"rendered":"

    Mongo \u805a\u5408\u65f6\u7684$max \u64cd\u4f5c…<\/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\/271830"}],"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=271830"}],"version-history":[{"count":0,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/271830\/revisions"}],"wp:attachment":[{"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=271830"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=271830"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=271830"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}