{"id":181288,"date":"2024-11-09T15:48:18","date_gmt":"2024-11-09T07:48:18","guid":{"rendered":"https:\/\/server.hk\/cnblog\/181288\/"},"modified":"2024-11-09T15:48:18","modified_gmt":"2024-11-09T07:48:18","slug":"%e6%b7%b1%e5%85%a5%e7%90%86%e8%a7%a3%e6%95%b8%e6%93%9a%e5%ba%ab%e8%aa%9e%e5%8f%a5select%e7%9a%84%e7%94%a8%e6%b3%95%e8%88%87%e5%84%aa%e5%8c%96%e6%8a%80%e5%b7%a7%ef%bc%88%e6%95%b8%e6%93%9a%e5%ba%ab","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/181288\/","title":{"rendered":"\u6df1\u5165\u7406\u89e3\u6578\u64da\u5eab\u8a9e\u53e5select\u7684\u7528\u6cd5\u8207\u512a\u5316\u6280\u5de7\uff08\u6578\u64da\u5eab\u8a9e\u53e5select\uff09"},"content":{"rendered":"<h1 id=\"%e6%b7%b1%e5%85%a5%e7%90%86%e8%a7%a3%e6%95%b8%e6%93%9a%e5%ba%ab%e8%aa%9e%e5%8f%a5select%e7%9a%84%e7%94%a8%e6%b3%95%e8%88%87%e5%84%aa%e5%8c%96%e6%8a%80%e5%b7%a7-ldXkDqGGtC\">\u6df1\u5165\u7406\u89e3\u6578\u64da\u5eab\u8a9e\u53e5SELECT\u7684\u7528\u6cd5\u8207\u512a\u5316\u6280\u5de7<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0c<code>SELECT<\/code> \u8a9e\u53e5\u662f\u6700\u5e38\u7528\u7684\u67e5\u8a62\u8a9e\u53e5\u4e4b\u4e00\u3002\u5b83\u5141\u8a31\u7528\u6236\u5f9e\u6578\u64da\u5eab\u4e2d\u6aa2\u7d22\u6578\u64da\uff0c\u4e26\u4e14\u53ef\u4ee5\u6839\u64da\u9700\u8981\u9032\u884c\u591a\u7a2e\u64cd\u4f5c\u548c\u904e\u6ffe\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e<code>SELECT<\/code> \u8a9e\u53e5\u7684\u57fa\u672c\u7528\u6cd5\u53ca\u5176\u512a\u5316\u6280\u5de7\uff0c\u5e6b\u52a9\u958b\u767c\u8005\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\u3002<\/p>\n<h2 id=\"1-select%e8%aa%9e%e5%8f%a5%e7%9a%84%e5%9f%ba%e6%9c%ac%e7%94%a8%e6%b3%95-ldXkDqGGtC\">1. SELECT\u8a9e\u53e5\u7684\u57fa\u672c\u7528\u6cd5<\/h2>\n<p><code>SELECT<\/code> \u8a9e\u53e5\u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT column1, column2, ...\nFROM table_name\nWHERE condition;<\/code><\/pre>\n<p>\u5728\u9019\u88e1\uff0c<code>column1, column2, ...<\/code> \u662f\u8981\u6aa2\u7d22\u7684\u5217\u540d\uff0c<code>table_name<\/code> \u662f\u6578\u64da\u8868\u7684\u540d\u7a31\uff0c\u800c<code>condition<\/code> \u662f\u904e\u6ffe\u689d\u4ef6\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u7c21\u55ae\u7684\u4f8b\u5b50\uff1a<\/p>\n<pre><code>SELECT name, age\nFROM users\nWHERE age &gt; 18;<\/code><\/pre>\n<p>\u9019\u689d\u8a9e\u53e5\u5c07\u5f9e<code>users<\/code> \u8868\u4e2d\u6aa2\u7d22\u6240\u6709\u5e74\u9f61\u5927\u65bc18\u6b72\u7684\u7528\u6236\u7684\u59d3\u540d\u548c\u5e74\u9f61\u3002<\/p>\n<h2 id=\"2-%e4%bd%bf%e7%94%a8distinct%e9%97%9c%e9%8d%b5%e5%ad%97-ldXkDqGGtC\">2. \u4f7f\u7528DISTINCT\u95dc\u9375\u5b57<\/h2>\n<p>\u7576\u9700\u8981\u5f9e\u6578\u64da\u8868\u4e2d\u6aa2\u7d22\u552f\u4e00\u503c\u6642\uff0c\u53ef\u4ee5\u4f7f\u7528<code>DISTINCT<\/code> \u95dc\u9375\u5b57\u3002\u9019\u6a23\u53ef\u4ee5\u907f\u514d\u91cd\u8907\u7684\u6578\u64da\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>SELECT DISTINCT country\nFROM users;<\/code><\/pre>\n<p>\u9019\u689d\u8a9e\u53e5\u5c07\u8fd4\u56de<code>users<\/code> \u8868\u4e2d\u6240\u6709\u4e0d\u540c\u7684\u570b\u5bb6\u540d\u7a31\u3002<\/p>\n<h2 id=\"3-%e6%8e%92%e5%ba%8f%e5%92%8c%e9%99%90%e5%88%b6%e7%b5%90%e6%9e%9c-ldXkDqGGtC\">3. \u6392\u5e8f\u548c\u9650\u5236\u7d50\u679c<\/h2>\n<p>\u53ef\u4ee5\u4f7f\u7528<code>ORDER BY<\/code> \u5b50\u53e5\u5c0d\u67e5\u8a62\u7d50\u679c\u9032\u884c\u6392\u5e8f\uff0c\u4e26\u4f7f\u7528<code>LIMIT<\/code> \u5b50\u53e5\u9650\u5236\u8fd4\u56de\u7684\u884c\u6578\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>SELECT name, age\nFROM users\nORDER BY age DESC\nLIMIT 5;<\/code><\/pre>\n<p>\u9019\u689d\u8a9e\u53e5\u5c07\u8fd4\u56de\u5e74\u9f61\u6700\u5927\u7684\u4e94\u4f4d\u7528\u6236\u7684\u59d3\u540d\u548c\u5e74\u9f61\u3002<\/p>\n<h2 id=\"4-join%e6%93%8d%e4%bd%9c-ldXkDqGGtC\">4. JOIN\u64cd\u4f5c<\/h2>\n<p>\u5728\u591a\u500b\u8868\u4e4b\u9593\u9032\u884c\u67e5\u8a62\u6642\uff0c\u53ef\u4ee5\u4f7f\u7528<code>JOIN<\/code> \u64cd\u4f5c\u3002\u9019\u4f7f\u5f97\u80fd\u5920\u6839\u64da\u5171\u540c\u7684\u5217\u4f86\u5408\u4f75\u6578\u64da\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>SELECT users.name, orders.amount\nFROM users\nJOIN orders ON users.id = orders.user_id;<\/code><\/pre>\n<p>\u9019\u689d\u8a9e\u53e5\u5c07\u8fd4\u56de\u6bcf\u4f4d\u7528\u6236\u53ca\u5176\u76f8\u61c9\u8a02\u55ae\u7684\u91d1\u984d\u3002<\/p>\n<h2 id=\"5-%e5%84%aa%e5%8c%96select%e8%aa%9e%e5%8f%a5%e7%9a%84%e6%8a%80%e5%b7%a7-ldXkDqGGtC\">5. \u512a\u5316SELECT\u8a9e\u53e5\u7684\u6280\u5de7<\/h2>\n<p>\u70ba\u4e86\u63d0\u9ad8<code>SELECT<\/code> \u8a9e\u53e5\u7684\u6027\u80fd\uff0c\u53ef\u4ee5\u63a1\u53d6\u4ee5\u4e0b\u5e7e\u500b\u512a\u5316\u6280\u5de7\uff1a<\/p>\n<ul>\n<li><strong>\u9078\u64c7\u5fc5\u8981\u7684\u5217\uff1a<\/strong>\u907f\u514d\u4f7f\u7528<code>SELECT *<\/code>\uff0c\u53ea\u9078\u64c7\u9700\u8981\u7684\u5217\uff0c\u9019\u6a23\u53ef\u4ee5\u6e1b\u5c11\u6578\u64da\u50b3\u8f38\u91cf\u3002<\/li>\n<li><strong>\u4f7f\u7528\u7d22\u5f15\uff1a<\/strong>\u70ba\u7d93\u5e38\u67e5\u8a62\u7684\u5217\u5275\u5efa\u7d22\u5f15\uff0c\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u67e5\u8a62\u901f\u5ea6\u3002<\/li>\n<li><strong>\u907f\u514d\u904e\u591a\u7684JOIN\uff1a<\/strong>\u904e\u591a\u7684JOIN\u64cd\u4f5c\u6703\u589e\u52a0\u67e5\u8a62\u7684\u8907\u96dc\u6027\u548c\u57f7\u884c\u6642\u9593\uff0c\u61c9\u76e1\u91cf\u7c21\u5316\u67e5\u8a62\u3002<\/li>\n<li><strong>\u4f7f\u7528WHERE\u689d\u4ef6\u904e\u6ffe\uff1a<\/strong>\u5728\u67e5\u8a62\u4e2d\u4f7f\u7528<code>WHERE<\/code> \u5b50\u53e5\u4f86\u904e\u6ffe\u4e0d\u5fc5\u8981\u7684\u6578\u64da\uff0c\u6e1b\u5c11\u7d50\u679c\u96c6\u7684\u5927\u5c0f\u3002<\/li>\n<li><strong>\u5b9a\u671f\u5206\u6790\u548c\u512a\u5316\u6578\u64da\u5eab\uff1a<\/strong>\u4f7f\u7528\u6578\u64da\u5eab\u63d0\u4f9b\u7684\u5de5\u5177\u5b9a\u671f\u5206\u6790\u67e5\u8a62\u6027\u80fd\uff0c\u4e26\u6839\u64da\u9700\u8981\u9032\u884c\u512a\u5316\u3002<\/li>\n<\/ul>\n<h2 id=\"6-%e7%b5%90%e8%ab%96-ldXkDqGGtC\">6. \u7d50\u8ad6<\/h2>\n<p>\u638c\u63e1<code>SELECT<\/code> \u8a9e\u53e5\u7684\u7528\u6cd5\u53ca\u5176\u512a\u5316\u6280\u5de7\u5c0d\u65bc\u6578\u64da\u5eab\u7ba1\u7406\u548c\u61c9\u7528\u958b\u767c\u81f3\u95dc\u91cd\u8981\u3002\u901a\u904e\u5408\u7406\u7684\u67e5\u8a62\u8a2d\u8a08\u548c\u512a\u5316\uff0c\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u6578\u64da\u6aa2\u7d22\u7684\u6548\u7387\uff0c\u5f9e\u800c\u63d0\u5347\u6574\u9ad4\u7cfb\u7d71\u7684\u6027\u80fd\u3002<\/p>\n<p>\u5982\u9700\u4e86\u89e3\u66f4\u591a\u95dc\u65bc<code>VPS<\/code> \u548c\u6578\u64da\u5eab\u7ba1\u7406\u7684\u8cc7\u8a0a\uff0c\u8acb\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9 <a href=\"https:\/\/server.hk\">Server.HK<\/a>\uff0c\u6211\u5011\u63d0\u4f9b\u5404\u7a2e<code>\u9999\u6e2fVPS<\/code> \u89e3\u6c7a\u65b9\u6848\uff0c\u52a9\u60a8\u8f15\u9b06\u7ba1\u7406\u6578\u64da\u5eab\u548c\u61c9\u7528\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6df1\u5165\u7406\u89e3\u6578\u64da\u5eab\u8a9e\u53e5SELECT\u7684\u7528\u6cd5\u8207\u512a\u5316\u6280\u5de7\uff0c\u63d0\u5347\u67e5\u8a62\u6548\u7387\uff0c\u638c\u63e1\u6578\u64da\u6aa2\u7d22\u7684\u95dc\u9375\u6280\u8853\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-181288","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/181288","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=181288"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/181288\/revisions"}],"predecessor-version":[{"id":181289,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/181288\/revisions\/181289"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=181288"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=181288"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=181288"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}