{"id":187696,"date":"2024-11-11T16:25:20","date_gmt":"2024-11-11T08:25:20","guid":{"rendered":"https:\/\/server.hk\/cnblog\/187696\/"},"modified":"2024-11-11T16:25:21","modified_gmt":"2024-11-11T08:25:21","slug":"%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%ad%e9%81%bf%e5%85%8dinner-join%e9%80%a3%e6%8e%a5%e8%a1%a8%e6%99%82%e5%87%ba%e7%8f%be%e9%87%8d%e8%a4%87%e6%95%b8%e6%93%9a%e7%9a%84%e6%96%b9%e6%b3%95","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/187696\/","title":{"rendered":"\u6578\u64da\u5eab\u4e2d\u907f\u514dINNER JOIN\u9023\u63a5\u8868\u6642\u51fa\u73fe\u91cd\u8907\u6578\u64da\u7684\u65b9\u6cd5"},"content":{"rendered":"<h1 id=\"%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%ad%e9%81%bf%e5%85%8dinner-join%e9%80%a3%e6%8e%a5%e8%a1%a8%e6%99%82%e5%87%ba%e7%8f%be%e9%87%8d%e8%a4%87%e6%95%b8%e6%93%9a%e7%9a%84%e6%96%b9%e6%b3%95-KWskUgixUg\">\u6578\u64da\u5eab\u4e2d\u907f\u514dINNER JOIN\u9023\u63a5\u8868\u6642\u51fa\u73fe\u91cd\u8907\u6578\u64da\u7684\u65b9\u6cd5<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u8a2d\u8a08\u548c\u67e5\u8a62\u4e2d\uff0cINNER JOIN\u662f\u4e00\u7a2e\u5e38\u7528\u7684\u64cd\u4f5c\uff0c\u7528\u65bc\u5f9e\u591a\u500b\u8868\u4e2d\u6aa2\u7d22\u76f8\u95dc\u6578\u64da\u3002\u7136\u800c\uff0c\u7576\u6578\u64da\u8868\u4e4b\u9593\u5b58\u5728\u591a\u5c0d\u591a\u7684\u95dc\u4fc2\u6642\uff0c\u4f7f\u7528INNER JOIN\u53ef\u80fd\u6703\u5c0e\u81f4\u91cd\u8907\u6578\u64da\u7684\u51fa\u73fe\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5728\u6578\u64da\u5eab\u4e2d\u907f\u514dINNER JOIN\u9023\u63a5\u8868\u6642\u51fa\u73fe\u91cd\u8907\u6578\u64da\u7684\u65b9\u6cd5\uff0c\u4e26\u63d0\u4f9b\u4e00\u4e9b\u5be6\u7528\u7684\u793a\u4f8b\u548c\u4ee3\u78bc\u7247\u6bb5\u3002<\/p>\n<h2 id=\"%e7%90%86%e8%a7%a3inner-join%e7%9a%84%e5%b7%a5%e4%bd%9c%e5%8e%9f%e7%90%86-KWskUgixUg\">\u7406\u89e3INNER JOIN\u7684\u5de5\u4f5c\u539f\u7406<\/h2>\n<p>INNER JOIN\u64cd\u4f5c\u6703\u6839\u64da\u6307\u5b9a\u7684\u689d\u4ef6\u5c07\u5169\u500b\u6216\u591a\u500b\u8868\u4e2d\u7684\u884c\u9032\u884c\u5339\u914d\u3002\u7576\u5339\u914d\u7684\u884c\u5b58\u5728\u591a\u500b\u6642\uff0c\u7d50\u679c\u96c6\u4e2d\u5c07\u51fa\u73fe\u91cd\u8907\u7684\u6578\u64da\u3002\u4f8b\u5982\uff0c\u8003\u616e\u4ee5\u4e0b\u5169\u500b\u8868\uff1a<\/p>\n<ul>\n<li><strong>\u5b78\u751f\u8868 (Students)<\/strong>\n<ul>\n<li>\u5b78\u751fID (StudentID)<\/li>\n<li>\u59d3\u540d (Name)<\/li>\n<\/ul>\n<\/li>\n<li><strong>\u8ab2\u7a0b\u8868 (Courses)<\/strong>\n<ul>\n<li>\u8ab2\u7a0bID (CourseID)<\/li>\n<li>\u5b78\u751fID (StudentID)<\/li>\n<li>\u8ab2\u7a0b\u540d\u7a31 (CourseName)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>\u5982\u679c\u4e00\u540d\u5b78\u751f\u9078\u4fee\u4e86\u591a\u9580\u8ab2\u7a0b\uff0c\u4f7f\u7528INNER JOIN\u67e5\u8a62\u5b78\u751f\u548c\u8ab2\u7a0b\u6642\uff0c\u5c07\u6703\u51fa\u73fe\u91cd\u8907\u7684\u5b78\u751f\u8a18\u9304\u3002<\/p>\n<h2 id=\"%e9%81%bf%e5%85%8d%e9%87%8d%e8%a4%87%e6%95%b8%e6%93%9a%e7%9a%84%e6%96%b9%e6%b3%95-KWskUgixUg\">\u907f\u514d\u91cd\u8907\u6578\u64da\u7684\u65b9\u6cd5<\/h2>\n<h3 id=\"1-%e4%bd%bf%e7%94%a8distinct%e9%97%9c%e9%8d%b5%e5%ad%97-KWskUgixUg\">1. \u4f7f\u7528DISTINCT\u95dc\u9375\u5b57<\/h3>\n<p>\u5728SQL\u67e5\u8a62\u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528DISTINCT\u95dc\u9375\u5b57\u4f86\u904e\u6ffe\u91cd\u8907\u7684\u884c\u3002\u9019\u6a23\u53ef\u4ee5\u78ba\u4fdd\u7d50\u679c\u96c6\u4e2d\u53ea\u8fd4\u56de\u552f\u4e00\u7684\u8a18\u9304\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>SELECT DISTINCT s.StudentID, s.Name\nFROM Students s\nINNER JOIN Courses c ON s.StudentID = c.StudentID;<\/code><\/pre>\n<p>\u9019\u6a23\u7684\u67e5\u8a62\u5c07\u53ea\u8fd4\u56de\u552f\u4e00\u7684\u5b78\u751fID\u548c\u59d3\u540d\uff0c\u800c\u4e0d\u6703\u91cd\u8907\u986f\u793a\u3002<\/p>\n<h3 id=\"2-%e4%bd%bf%e7%94%a8group-by%e5%ad%90%e5%8f%a5-KWskUgixUg\">2. \u4f7f\u7528GROUP BY\u5b50\u53e5<\/h3>\n<p>\u53e6\u4e00\u7a2e\u907f\u514d\u91cd\u8907\u6578\u64da\u7684\u65b9\u6cd5\u662f\u4f7f\u7528GROUP BY\u5b50\u53e5\u3002\u9019\u53ef\u4ee5\u6839\u64da\u7279\u5b9a\u7684\u5217\u9032\u884c\u5206\u7d44\uff0c\u4e26\u4f7f\u7528\u805a\u5408\u51fd\u6578\u4f86\u7372\u53d6\u6240\u9700\u7684\u6578\u64da\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>SELECT s.StudentID, s.Name, COUNT(c.CourseID) AS CourseCount\nFROM Students s\nINNER JOIN Courses c ON s.StudentID = c.StudentID\nGROUP BY s.StudentID, s.Name;<\/code><\/pre>\n<p>\u9019\u6a23\u7684\u67e5\u8a62\u5c07\u8fd4\u56de\u6bcf\u4f4d\u5b78\u751f\u7684\u552f\u4e00\u8a18\u9304\uff0c\u4e26\u986f\u793a\u4ed6\u5011\u9078\u4fee\u7684\u8ab2\u7a0b\u6578\u91cf\u3002<\/p>\n<h3 id=\"3-%e4%bd%bf%e7%94%a8%e5%ad%90%e6%9f%a5%e8%a9%a2-KWskUgixUg\">3. \u4f7f\u7528\u5b50\u67e5\u8a62<\/h3>\n<p>\u5b50\u67e5\u8a62\u53ef\u4ee5\u7528\u4f86\u5148\u7372\u53d6\u552f\u4e00\u7684\u8a18\u9304\uff0c\u7136\u5f8c\u518d\u9032\u884cJOIN\u64cd\u4f5c\u3002\u9019\u6a23\u53ef\u4ee5\u6709\u6548\u5730\u907f\u514d\u91cd\u8907\u6578\u64da\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>SELECT s.StudentID, s.Name\nFROM Students s\nWHERE s.StudentID IN (SELECT DISTINCT StudentID FROM Courses);<\/code><\/pre>\n<p>\u9019\u6a23\u7684\u67e5\u8a62\u5c07\u53ea\u8fd4\u56de\u90a3\u4e9b\u81f3\u5c11\u9078\u4fee\u4e86\u4e00\u9580\u8ab2\u7a0b\u7684\u5b78\u751f\u3002<\/p>\n<h3 id=\"4-%e4%bd%bf%e7%94%a8cte%ef%bc%88%e5%85%ac%e7%94%a8%e8%a1%a8%e8%a1%a8%e9%81%94%e5%bc%8f%ef%bc%89-KWskUgixUg\">4. \u4f7f\u7528CTE\uff08\u516c\u7528\u8868\u8868\u9054\u5f0f\uff09<\/h3>\n<p>\u516c\u7528\u8868\u8868\u9054\u5f0f\uff08CTE\uff09\u662f\u4e00\u7a2e\u66f4\u70ba\u9748\u6d3b\u7684\u65b9\u5f0f\u4f86\u8655\u7406\u8907\u96dc\u7684\u67e5\u8a62\u3002\u4f7f\u7528CTE\u53ef\u4ee5\u5148\u5b9a\u7fa9\u4e00\u500b\u552f\u4e00\u7684\u6578\u64da\u96c6\uff0c\u7136\u5f8c\u518d\u9032\u884cJOIN\u64cd\u4f5c\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>WITH UniqueStudents AS (\n    SELECT DISTINCT StudentID, Name\n    FROM Students\n)\nSELECT u.StudentID, u.Name\nFROM UniqueStudents u\nINNER JOIN Courses c ON u.StudentID = c.StudentID;<\/code><\/pre>\n<p>\u9019\u6a23\u7684\u67e5\u8a62\u5c07\u78ba\u4fdd\u7d50\u679c\u96c6\u4e2d\u4e0d\u6703\u51fa\u73fe\u91cd\u8907\u7684\u5b78\u751f\u8a18\u9304\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-KWskUgixUg\">\u7e3d\u7d50<\/h2>\n<p>\u5728\u6578\u64da\u5eab\u4e2d\uff0c\u907f\u514dINNER JOIN\u9023\u63a5\u8868\u6642\u51fa\u73fe\u91cd\u8907\u6578\u64da\u662f\u975e\u5e38\u91cd\u8981\u7684\uff0c\u7279\u5225\u662f\u5728\u8655\u7406\u591a\u5c0d\u591a\u95dc\u4fc2\u6642\u3002\u901a\u904e\u4f7f\u7528DISTINCT\u3001GROUP BY\u3001\u5b50\u67e5\u8a62\u548cCTE\u7b49\u65b9\u6cd5\uff0c\u53ef\u4ee5\u6709\u6548\u5730\u904e\u6ffe\u91cd\u8907\u6578\u64da\uff0c\u78ba\u4fdd\u67e5\u8a62\u7d50\u679c\u7684\u6e96\u78ba\u6027\u548c\u53ef\u8b80\u6027\u3002\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u8655\u7406\u7684\u61c9\u7528\uff0c\u9078\u64c7\u5408\u9069\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\u81f3\u95dc\u91cd\u8981\u3002\u82e5\u60a8\u5c0d\u65bc<em><a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a><\/em>\u6216<em><a href=\"https:\/\/server.hk\">\u96f2\u4f3a\u670d\u5668<\/a><\/em>\u6709\u8208\u8da3\uff0c\u8acb\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4ee5\u7372\u53d6\u66f4\u591a\u4fe1\u606f\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22\u907f\u514d\u6578\u64da\u5eab\u4e2dINNER JOIN\u9023\u63a5\u8868\u6642\u51fa\u73fe\u91cd\u8907\u6578\u64da\u7684\u65b9\u6cd5\uff0c\u63d0\u5347\u67e5\u8a62\u6548\u7387\u8207\u6578\u64da\u6e96\u78ba\u6027\u3002<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-187696","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/187696","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"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=187696"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/187696\/revisions"}],"predecessor-version":[{"id":187697,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/187696\/revisions\/187697"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=187696"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=187696"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=187696"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}