{"id":144073,"date":"2024-11-01T04:47:28","date_gmt":"2024-10-31T20:47:28","guid":{"rendered":"https:\/\/server.hk\/cnblog\/144073\/"},"modified":"2024-11-01T04:47:29","modified_gmt":"2024-10-31T20:47:29","slug":"sql-%e8%aa%9e%e5%8f%a5%e4%b8%ad%e7%9a%84-select-distinct","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/144073\/","title":{"rendered":"SQL \u8a9e\u53e5\u4e2d\u7684 SELECT DISTINCT"},"content":{"rendered":"<h1 id=\"sql-%e8%aa%9e%e5%8f%a5%e4%b8%ad%e7%9a%84-select-distinct-poZfkRjMGY\">SQL \u8a9e\u53e5\u4e2d\u7684 SELECT DISTINCT<\/h1>\n<p>\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0cSQL\uff08\u7d50\u69cb\u5316\u67e5\u8a62\u8a9e\u8a00\uff09\u662f\u4e00\u7a2e\u7528\u65bc\u67e5\u8a62\u548c\u64cd\u4f5c\u8cc7\u6599\u7684\u6a19\u6e96\u8a9e\u8a00\u3002\u7576\u6211\u5011\u9700\u8981\u5f9e\u8cc7\u6599\u8868\u4e2d\u7372\u53d6\u552f\u4e00\u7684\u8cc7\u6599\u6642\uff0c<code>SELECT DISTINCT<\/code> \u8a9e\u53e5\u4fbf\u6210\u70ba\u4e00\u500b\u975e\u5e38\u6709\u7528\u7684\u5de5\u5177\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e <code>SELECT DISTINCT<\/code> \u7684\u7528\u6cd5\u3001\u529f\u80fd\u53ca\u5176\u5728\u5be6\u969b\u61c9\u7528\u4e2d\u7684\u91cd\u8981\u6027\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%af-select-distinct%ef%bc%9f-poZfkRjMGY\">\u4ec0\u9ebc\u662f SELECT DISTINCT\uff1f<\/h2>\n<p><code>SELECT DISTINCT<\/code> \u662f\u4e00\u500b SQL \u8a9e\u53e5\uff0c\u7528\u65bc\u5f9e\u8cc7\u6599\u8868\u4e2d\u9078\u53d6\u4e0d\u91cd\u8907\u7684\u8cc7\u6599\u884c\u3002\u9019\u610f\u5473\u8457\u7576\u6211\u5011\u67e5\u8a62\u67d0\u500b\u6b04\u4f4d\u6642\uff0c<code>SELECT DISTINCT<\/code> \u6703\u904e\u6ffe\u6389\u6240\u6709\u91cd\u8907\u7684\u503c\uff0c\u53ea\u8fd4\u56de\u552f\u4e00\u7684\u7d50\u679c\u3002\u9019\u5728\u8655\u7406\u5927\u91cf\u8cc7\u6599\u6642\u7279\u5225\u6709\u7528\uff0c\u56e0\u70ba\u5b83\u53ef\u4ee5\u5e6b\u52a9\u6211\u5011\u5feb\u901f\u8b58\u5225\u8cc7\u6599\u4e2d\u7684\u7368\u7279\u9805\u76ee\u3002<\/p>\n<h2 id=\"select-distinct-%e7%9a%84%e5%9f%ba%e6%9c%ac%e8%aa%9e%e6%b3%95-poZfkRjMGY\">SELECT DISTINCT \u7684\u57fa\u672c\u8a9e\u6cd5<\/h2>\n<p>\u4f7f\u7528 <code>SELECT DISTINCT<\/code> \u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT DISTINCT column1, column2, ...\nFROM table_name;\n<\/code><\/pre>\n<p>\u5728\u9019\u88e1\uff0c<code>column1, column2, ...<\/code> \u662f\u6211\u5011\u5e0c\u671b\u67e5\u8a62\u7684\u6b04\u4f4d\uff0c\u800c <code>table_name<\/code> \u5247\u662f\u8cc7\u6599\u8868\u7684\u540d\u7a31\u3002<\/p>\n<h2 id=\"%e4%bd%bf%e7%94%a8%e7%af%84%e4%be%8b-poZfkRjMGY\">\u4f7f\u7528\u7bc4\u4f8b<\/h2>\n<p>\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba <code>Customers<\/code> \u7684\u8cc7\u6599\u8868\uff0c\u8a72\u8868\u5305\u542b\u4ee5\u4e0b\u6b04\u4f4d\uff1a<\/p>\n<ul>\n<li>CustomerID<\/li>\n<li>CustomerName<\/li>\n<li>Country<\/li>\n<\/ul>\n<p>\u5982\u679c\u6211\u5011\u60f3\u8981\u67e5\u8a62\u6240\u6709\u7368\u7279\u7684\u570b\u5bb6\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b SQL \u8a9e\u53e5\uff1a<\/p>\n<pre><code>SELECT DISTINCT Country\nFROM Customers;\n<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u4e0d\u540c\u7684\u570b\u5bb6\u540d\u7a31\uff0c\u800c\u4e0d\u6703\u91cd\u8907\u986f\u793a\u76f8\u540c\u7684\u570b\u5bb6\u3002<\/p>\n<h2 id=\"%e5%a4%9a%e6%ac%84%e4%bd%8d%e7%9a%84-distinct-poZfkRjMGY\">\u591a\u6b04\u4f4d\u7684 DISTINCT<\/h2>\n<p>\u9664\u4e86\u55ae\u4e00\u6b04\u4f4d\u5916\uff0c\u6211\u5011\u4e5f\u53ef\u4ee5\u5728\u591a\u500b\u6b04\u4f4d\u4e0a\u4f7f\u7528 <code>SELECT DISTINCT<\/code>\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u5011\u60f3\u8981\u67e5\u8a62\u6bcf\u500b\u570b\u5bb6\u548c\u5ba2\u6236\u540d\u7a31\u7684\u7368\u7279\u7d44\u5408\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u8a9e\u53e5\uff1a<\/p>\n<pre><code>SELECT DISTINCT Country, CustomerName\nFROM Customers;\n<\/code><\/pre>\n<p>\u9019\u6a23\u7684\u67e5\u8a62\u5c07\u8fd4\u56de\u6bcf\u500b\u570b\u5bb6\u4e2d\u6240\u6709\u7368\u7279\u7684\u5ba2\u6236\u540d\u7a31\u7d44\u5408\u3002<\/p>\n<h2 id=\"%e6%b3%a8%e6%84%8f%e4%ba%8b%e9%a0%85-poZfkRjMGY\">\u6ce8\u610f\u4e8b\u9805<\/h2>\n<p>\u5728\u4f7f\u7528 <code>SELECT DISTINCT<\/code> \u6642\uff0c\u6709\u5e7e\u9ede\u9700\u8981\u6ce8\u610f\uff1a<\/p>\n<ul>\n<li><strong>\u6027\u80fd\u554f\u984c\uff1a<\/strong>\u7576\u8cc7\u6599\u8868\u975e\u5e38\u9f90\u5927\u6642\uff0c\u4f7f\u7528 <code>SELECT DISTINCT<\/code> \u53ef\u80fd\u6703\u5f71\u97ff\u67e5\u8a62\u6027\u80fd\uff0c\u56e0\u70ba\u7cfb\u7d71\u9700\u8981\u9032\u884c\u984d\u5916\u7684\u8a08\u7b97\u4f86\u904e\u6ffe\u91cd\u8907\u7684\u8cc7\u6599\u3002<\/li>\n<li><strong>NULL \u503c\uff1a<\/strong>\u5728\u4f7f\u7528 <code>SELECT DISTINCT<\/code> \u6642\uff0cNULL \u503c\u4e5f\u6703\u88ab\u8996\u70ba\u4e00\u500b\u7368\u7279\u7684\u503c\uff0c\u56e0\u6b64\u5982\u679c\u8cc7\u6599\u4e2d\u5b58\u5728 NULL\uff0c\u5247\u67e5\u8a62\u7d50\u679c\u4e2d\u4e5f\u6703\u5305\u542b NULL\u3002<\/li>\n<li><strong>\u6392\u5e8f\uff1a<\/strong>\u5982\u679c\u9700\u8981\u5c0d\u7d50\u679c\u9032\u884c\u6392\u5e8f\uff0c\u53ef\u4ee5\u7d50\u5408 <code>ORDER BY<\/code> \u8a9e\u53e5\u4f7f\u7528\uff0c\u4f8b\u5982\uff1a<code>SELECT DISTINCT Country FROM Customers ORDER BY Country;<\/code><\/li>\n<\/ul>\n<h2 id=\"%e7%b8%bd%e7%b5%90-poZfkRjMGY\">\u7e3d\u7d50<\/h2>\n<p>\u5728 SQL \u8a9e\u53e5\u4e2d\uff0c<code>SELECT DISTINCT<\/code> \u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u80fd\u5920\u5e6b\u52a9\u6211\u5011\u5f9e\u8cc7\u6599\u8868\u4e2d\u63d0\u53d6\u552f\u4e00\u7684\u8cc7\u6599\u884c\u3002\u7121\u8ad6\u662f\u5728\u6578\u64da\u5206\u6790\u9084\u662f\u5831\u544a\u751f\u6210\u4e2d\uff0c\u9019\u500b\u529f\u80fd\u90fd\u80fd\u5920\u63d0\u4f9b\u91cd\u8981\u7684\u6d1e\u898b\u3002\u4e86\u89e3\u5982\u4f55\u6709\u6548\u5730\u4f7f\u7528 <code>SELECT DISTINCT<\/code> \u5c0d\u65bc\u4efb\u4f55\u8cc7\u6599\u5eab\u7ba1\u7406\u8005\u6216\u958b\u767c\u8005\u4f86\u8aaa\u90fd\u662f\u4e00\u9805\u57fa\u672c\u6280\u80fd\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684 <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u89e3\u6c7a\u65b9\u6848\uff0cServer.HK \u63d0\u4f9b\u591a\u7a2e\u9078\u64c7\uff0c\u6eff\u8db3\u60a8\u7684\u9700\u6c42\u3002\u7121\u8ad6\u662f\u8cc7\u6599\u5eab\u7ba1\u7406\u9084\u662f\u7db2\u7ad9\u6258\u7ba1\uff0c\u6211\u5011\u7684 <a href=\"https:\/\/server.hk\">\u4f3a\u670d\u5668<\/a> \u90fd\u80fd\u70ba\u60a8\u63d0\u4f9b\u7a69\u5b9a\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3 SQL \u8a9e\u53e5\u4e2d\u7684 SELECT DISTINCT\uff0c\u5b78\u7fd2\u5982\u4f55\u5f9e\u8cc7\u6599\u5eab\u4e2d\u9078\u53d6\u552f\u4e00\u503c\uff0c\u907f\u514d\u91cd\u8907\u6578\u64da\uff0c\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\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-144073","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/144073","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=144073"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/144073\/revisions"}],"predecessor-version":[{"id":144074,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/144073\/revisions\/144074"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=144073"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=144073"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=144073"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}