{"id":20335,"date":"2024-01-02T04:28:23","date_gmt":"2024-01-02T04:28:23","guid":{"rendered":"https:\/\/server.hk\/blog\/20335\/"},"modified":"2024-11-14T10:40:14","modified_gmt":"2024-11-14T02:40:14","slug":"postgresql-command-select","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/20335\/","title":{"rendered":"PostgreSQL \u6307\u4ee4\uff1aSELECT"},"content":{"rendered":"<h1 id=\"postgresql-command-select-MZBLjfXNgf\">PostgreSQL \u6307\u4ee4\uff1aSELECT<\/h1>\n<p>PostgreSQL \u662f\u4e00\u500b\u5f37\u5927\u7684\u958b\u6e90\u95dc\u806f\u5f0f\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\uff0c\u63d0\u4f9b\u591a\u7a2e\u529f\u80fd\u53ca\u80fd\u529b\u3002<code>SELECT<\/code> \u6307\u4ee4\u662f PostgreSQL \u4e2d\u6700\u5e38\u7528\u7684\u6307\u4ee4\u4e4b\u4e00\u3002\u5728\u672c\u6587\u4e2d\uff0c\u6211\u5011\u5c07\u8a73\u7d30\u63a2\u8a0e <code>SELECT<\/code> \u6307\u4ee4\uff0c\u4e26\u4e86\u89e3\u5982\u4f55\u4f7f\u7528\u5b83\u4f86\u5f9e PostgreSQL \u8cc7\u6599\u5eab\u4e2d\u6aa2\u7d22\u6578\u64da\u3002<\/p>\n<h2 id=\"introduction-to-the-select-command-MZBLjfXNgf\">SELECT \u6307\u4ee4\u7c21\u4ecb<\/h2>\n<p><code>SELECT<\/code> \u6307\u4ee4\u7528\u65bc\u5f9e PostgreSQL \u8cc7\u6599\u5eab\u4e2d\u7684\u4e00\u500b\u6216\u591a\u500b\u8868\u683c\u4e2d\u67e5\u8a62\u6578\u64da\u3002\u5b83\u5141\u8a31\u60a8\u6307\u5b9a\u8981\u6aa2\u7d22\u7684\u6b04\u4f4d\u3001\u61c9\u7528\u7be9\u9078\u689d\u4ef6\u4ee5\u7e2e\u5c0f\u7d50\u679c\u7bc4\u570d\uff0c\u4e26\u6839\u64da\u7279\u5b9a\u7684\u9806\u5e8f\u5c0d\u6578\u64da\u9032\u884c\u6392\u5e8f\u3002<code>SELECT<\/code> \u6307\u4ee4\u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT column1, column2, ...\r\nFROM table_name\r\nWHERE condition\r\nORDER BY column_name;<\/code><\/pre>\n<p>\u4ee5\u4e0b\u662f\u5c0d <code>SELECT<\/code> \u6307\u4ee4\u5404\u7d44\u6210\u90e8\u5206\u7684\u89e3\u91cb\uff1a<\/p>\n<ul>\n<li><code>column1, column2, ...<\/code>\uff1a\u9019\u4e9b\u662f\u60a8\u60f3\u5f9e\u8868\u683c\u4e2d\u6aa2\u7d22\u7684\u6b04\u4f4d\u3002\u60a8\u53ef\u4ee5\u6307\u5b9a\u591a\u500b\u6b04\u4f4d\uff0c\u4e26\u7528\u9017\u865f\u5206\u9694\uff0c\u6216\u4f7f\u7528\u661f\u865f\uff08*\uff09\u4f86\u9078\u64c7\u6240\u6709\u6b04\u4f4d\u3002<\/li>\n<li><code>table_name<\/code>\uff1a\u9019\u662f\u60a8\u60f3\u8981\u6aa2\u7d22\u6578\u64da\u7684\u8868\u683c\u540d\u7a31\u3002<\/li>\n<li><code>condition<\/code>\uff1a\u9019\u662f\u53ef\u9078\u7684\u53c3\u6578\uff0c\u5141\u8a31\u60a8\u5c0d\u6578\u64da\u61c9\u7528\u7be9\u9078\u689d\u4ef6\u3002\u60a8\u53ef\u4ee5\u4f7f\u7528\u6bd4\u8f03\u904b\u7b97\u7b26\u3001\u908f\u8f2f\u904b\u7b97\u7b26\u53ca\u5176\u4ed6\u689d\u4ef6\u4f86\u6307\u5b9a\u7be9\u9078\u6a19\u6e96\u3002<\/li>\n<li><code>ORDER BY column_name<\/code>\uff1a\u9019\u662f\u53ef\u9078\u7684\u53c3\u6578\uff0c\u5141\u8a31\u60a8\u6839\u64da\u6307\u5b9a\u6b04\u4f4d\u6309\u5347\u5e8f\u6216\u964d\u5e8f\u6392\u5e8f\u6578\u64da\u3002<\/li>\n<\/ul>\n<h2 id=\"examples-of-using-the-select-command-MZBLjfXNgf\">\u4f7f\u7528 SELECT \u6307\u4ee4\u7684\u7bc4\u4f8b<\/h2>\n<p>\u6211\u5011\u4f86\u770b\u770b\u4e00\u4e9b\u7bc4\u4f8b\uff0c\u4ee5\u4e86\u89e3 <code>SELECT<\/code> \u6307\u4ee4\u7684\u4f7f\u7528\u65b9\u6cd5\uff1a<\/p>\n<h3 id=\"example-1-retrieving-all-columns-MZBLjfXNgf\">\u7bc4\u4f8b 1\uff1a\u6aa2\u7d22\u6240\u6709\u6b04\u4f4d<\/h3>\n<pre><code>SELECT *\r\nFROM employees;<\/code><\/pre>\n<p>\u6b64\u67e5\u8a62\u5c07\u5f9e &#8220;employees&#8221; \u8868\u683c\u4e2d\u6aa2\u7d22\u6240\u6709\u6b04\u4f4d\u3002<\/p>\n<h3 id=\"example-2-retrieving-specific-columns-MZBLjfXNgf\">\u7bc4\u4f8b 2\uff1a\u6aa2\u7d22\u7279\u5b9a\u6b04\u4f4d<\/h3>\n<pre><code>SELECT first_name, last_name, email\r\nFROM employees;<\/code><\/pre>\n<p>\u6b64\u67e5\u8a62\u53ea\u6703\u5f9e &#8220;employees&#8221; \u8868\u683c\u4e2d\u6aa2\u7d22 &#8220;first_name&#8221;\u3001&#8221;last_name&#8221; \u548c &#8220;email&#8221; \u6b04\u4f4d\u3002<\/p>\n<h3 id=\"example-3-applying-filters-MZBLjfXNgf\">\u7bc4\u4f8b 3\uff1a\u61c9\u7528\u7be9\u9078\u689d\u4ef6<\/h3>\n<pre><code>SELECT *\r\nFROM employees\r\nWHERE salary &gt; 50000;<\/code><\/pre>\n<p>\u6b64\u67e5\u8a62\u6703\u6aa2\u7d22 &#8220;employees&#8221; \u8868\u683c\u4e2d\u85aa\u6c34\u5927\u65bc 50000 \u7684\u6240\u6709\u6b04\u4f4d\u3002<\/p>\n<h3 id=\"example-4-sorting-data-MZBLjfXNgf\">\u7bc4\u4f8b 4\uff1a\u6392\u5e8f\u6578\u64da<\/h3>\n<pre><code>SELECT *\r\nFROM employees\r\nORDER BY hire_date DESC;<\/code><\/pre>\n<p>\u6b64\u67e5\u8a62\u6703\u6aa2\u7d22 &#8220;employees&#8221; \u8868\u683c\u4e2d\u7684\u6240\u6709\u6b04\u4f4d\uff0c\u4e26\u6839\u64da &#8220;hire_date&#8221; \u6b04\u4f4d\u4ee5\u964d\u5e8f\u6392\u5e8f\u6578\u64da\u3002<\/p>\n<h2 id=\"conclusion-MZBLjfXNgf\">\u7d50\u8ad6<\/h2>\n<p><code>SELECT<\/code> \u6307\u4ee4\u662f PostgreSQL \u4e2d\u4e00\u500b\u57fa\u672c\u7684\u5de5\u5177\uff0c\u5141\u8a31\u60a8\u6839\u64da\u7279\u5b9a\u689d\u4ef6\u5f9e\u8868\u683c\u4e2d\u6aa2\u7d22\u6578\u64da\u3002\u901a\u904e\u7406\u89e3\u5176\u8a9e\u6cd5\u53ca\u5404\u7a2e\u9078\u9805\uff0c\u60a8\u53ef\u4ee5\u6709\u6548\u5730\u67e5\u8a62 PostgreSQL \u8cc7\u6599\u5eab\uff0c\u4e26\u7372\u53d6\u6240\u9700\u7684\u4fe1\u606f\u3002\u4e0d\u8ad6\u662f\u6aa2\u7d22\u6240\u6709\u6b04\u4f4d\u3001\u7279\u5b9a\u6b04\u4f4d\u3001\u61c9\u7528\u7be9\u9078\u689d\u4ef6\uff0c\u9084\u662f\u5c0d\u6578\u64da\u9032\u884c\u6392\u5e8f\uff0c<code>SELECT<\/code> \u6307\u4ee4\u90fd\u80fd\u70ba\u60a8\u63d0\u4f9b\u6eff\u8db3\u9700\u6c42\u7684\u9748\u6d3b\u6027\u3002<\/p>\n<h2 id=\"summary-MZBLjfXNgf\">\u7e3d\u7d50<\/h2>\n<p>\u7e3d\u800c\u8a00\u4e4b\uff0cPostgreSQL \u4e2d\u7684 <code>SELECT<\/code> \u6307\u4ee4\u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u7528\u65bc\u5f9e\u8868\u683c\u4e2d\u6aa2\u7d22\u6578\u64da\u3002\u5b83\u5141\u8a31\u60a8\u6307\u5b9a\u8981\u6aa2\u7d22\u7684\u6b04\u4f4d\u3001\u61c9\u7528\u7be9\u9078\u689d\u4ef6\u53ca\u6392\u5e8f\u6578\u64da\u3002\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u53ef\u9760\u4e14\u9ad8\u6548\u80fd\u7684 VPS \u8a17\u7ba1\u89e3\u6c7a\u65b9\u6848\uff0c\u8acb\u8003\u616e <a href=\"https:\/\/server.hk\">Server.HK<\/a>\u3002\u4ed6\u5011\u63d0\u4f9b\u591a\u6a23\u5316\u7684\u65b9\u6848\u53ca\u5353\u8d8a\u7684\u5ba2\u6236\u652f\u6301\uff0c\u662f\u696d\u754c\u53d7\u4fe1\u8cf4\u7684\u63d0\u4f9b\u5546\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>PostgreSQL \u6307\u4ee4\uff1aSE&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4924],"tags":[],"class_list":["post-20335","post","type-post","status-publish","format-standard","hentry","category-setup-tutorials"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/20335","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"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=20335"}],"version-history":[{"count":3,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/20335\/revisions"}],"predecessor-version":[{"id":24432,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/20335\/revisions\/24432"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=20335"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=20335"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=20335"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}