{"id":20759,"date":"2024-01-02T05:28:19","date_gmt":"2024-01-02T05:28:19","guid":{"rendered":"https:\/\/server.hk\/blog\/20759\/"},"modified":"2024-11-14T10:39:12","modified_gmt":"2024-11-14T02:39:12","slug":"postgresql-command-drop-cast","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/20759\/","title":{"rendered":"PostgreSQL \u6307\u4ee4\uff1aDROP CAST"},"content":{"rendered":"<h1 id=\"postgresql-command-drop-cast-PogQvDoenf\">PostgreSQL \u6307\u4ee4\uff1aDROP CAST<\/h1>\n<p>PostgreSQL \u662f\u4e00\u500b\u529f\u80fd\u5f37\u5927\u7684\u958b\u6e90\u95dc\u4fc2\u578b\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\uff0c\u63d0\u4f9b\u4e86\u5ee3\u6cdb\u7684\u529f\u80fd\u548c\u7279\u9ede\u3002\u5176\u4e2d\u4e00\u500b\u91cd\u8981\u7684\u6307\u4ee4\u662f <code>DROP CAST<\/code> \u6307\u4ee4\uff0c\u5141\u8a31\u7528\u6236\u79fb\u9664\u5169\u500b\u8cc7\u6599\u985e\u578b\u4e4b\u9593\u7684\u8f49\u63db\u3002\u5728\u672c\u6587\u4e2d\uff0c\u6211\u5011\u5c07\u63a2\u8a0e <code>DROP CAST<\/code> \u6307\u4ee4\u53ca\u5176\u5728 PostgreSQL \u4e2d\u7684\u7528\u6cd5\u3002<\/p>\n<h2 id=\"understanding-cast-in-postgresql-PogQvDoenf\">\u4e86\u89e3 PostgreSQL \u4e2d\u7684 CAST<\/h2>\n<p>\u5728 PostgreSQL \u4e2d\uff0c<code>CAST<\/code> \u51fd\u6578\u7528\u65bc\u5c07\u4e00\u7a2e\u8cc7\u6599\u985e\u578b\u8f49\u63db\u70ba\u53e6\u4e00\u7a2e\u8cc7\u6599\u985e\u578b\u3002\u5b83\u5141\u8a31\u7528\u6236\u57f7\u884c\u660e\u78ba\u7684\u985e\u578b\u8f49\u63db\uff0c\u5f9e\u800c\u78ba\u4fdd\u4e0d\u540c\u8cc7\u6599\u985e\u578b\u4e4b\u9593\u7684\u517c\u5bb9\u6027\u3002<code>CAST<\/code> \u53ef\u4ee5\u7528\u65bc\u591a\u7a2e\u60c5\u5883\uff0c\u4f8b\u5982\u5c07\u5b57\u4e32\u8f49\u63db\u70ba\u6574\u6578\u6216\u5c07\u65e5\u671f\u8f49\u63db\u70ba\u6642\u9593\u6233\u3002<\/p>\n<p>\u7576\u5728\u5169\u500b\u8cc7\u6599\u985e\u578b\u4e4b\u9593\u5275\u5efa\u4e00\u500b\u8f49\u63db\u6642\uff0cPostgreSQL \u6703\u5c07\u8a72\u8f49\u63db\u7684\u4fe1\u606f\u5132\u5b58\u5728\u7cfb\u7d71\u76ee\u9304\u4e2d\u3002\u9019\u4e9b\u4fe1\u606f\u5305\u62ec\u4f86\u6e90\u548c\u76ee\u6a19\u8cc7\u6599\u985e\u578b\uff0c\u4ee5\u53ca\u7528\u65bc\u8f49\u63db\u7684\u51fd\u6578\u3002<code>DROP CAST<\/code> \u6307\u4ee4\u5141\u8a31\u7528\u6236\u5f9e\u7cfb\u7d71\u76ee\u9304\u4e2d\u79fb\u9664\u9019\u4e9b\u8f49\u63db\u4fe1\u606f\u3002<\/p>\n<h2 id=\"syntax-of-drop-cast-command-PogQvDoenf\">DROP CAST \u6307\u4ee4\u7684\u8a9e\u6cd5<\/h2>\n<p>PostgreSQL \u4e2d <code>DROP CAST<\/code> \u6307\u4ee4\u7684\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>DROP CAST (source_type AS target_type)\r\n<\/code><\/pre>\n<p>\u5176\u4e2d\uff0c<code>source_type<\/code> \u4ee3\u8868\u4f86\u6e90\u8cc7\u6599\u985e\u578b\uff0c<code>target_type<\/code> \u4ee3\u8868\u76ee\u6a19\u8cc7\u6599\u985e\u578b\u3002\u7576\u57f7\u884c <code>DROP CAST<\/code> \u6307\u4ee4\u6642\uff0cPostgreSQL \u6703\u79fb\u9664\u5f9e <code>source_type<\/code> \u5230 <code>target_type<\/code> \u7684\u8f49\u63db\u3002<\/p>\n<h2 id=\"example-PogQvDoenf\">\u7bc4\u4f8b<\/h2>\n<p>\u8b93\u6211\u5011\u4f86\u770b\u4e00\u500b\u7bc4\u4f8b\uff0c\u6211\u5011\u6709\u4e00\u500b\u5f9e <code>text<\/code> \u8cc7\u6599\u985e\u578b\u5230 <code>integer<\/code> \u8cc7\u6599\u985e\u578b\u7684\u8f49\u63db\u3002\u6211\u5011\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u6307\u4ee4\u4f86\u5275\u5efa\u9019\u500b\u8f49\u63db\uff1a<\/p>\n<pre><code>CREATE CAST (text AS integer) WITH FUNCTION text_to_integer(text) AS ASSIGNMENT;\r\n<\/code><\/pre>\n<p>\u73fe\u5728\uff0c\u5982\u679c\u6211\u5011\u60f3\u8981\u79fb\u9664\u9019\u500b\u8f49\u63db\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b <code>DROP CAST<\/code> \u6307\u4ee4\uff1a<\/p>\n<pre><code>DROP CAST (text AS integer);\r\n<\/code><\/pre>\n<p>\u57f7\u884c\u6b64\u6307\u4ee4\u5c07\u5f9e\u7cfb\u7d71\u76ee\u9304\u4e2d\u79fb\u9664\u5f9e <code>text<\/code> \u5230 <code>integer<\/code> \u7684\u8f49\u63db\u3002<\/p>\n<h2 id=\"conclusion-PogQvDoenf\">\u7d50\u8ad6<\/h2>\n<p>PostgreSQL \u4e2d\u7684 <code>DROP CAST<\/code> \u6307\u4ee4\u662f\u4e00\u500b\u7528\u65bc\u79fb\u9664\u4e0d\u540c\u8cc7\u6599\u985e\u578b\u4e4b\u9593\u8f49\u63db\u7684\u6709\u7528\u5de5\u5177\u3002\u5b83\u5141\u8a31\u7528\u6236\u7ba1\u7406\u7cfb\u7d71\u76ee\u9304\u4e2d\u5132\u5b58\u7684\u8f49\u63db\u4fe1\u606f\uff0c\u5f9e\u800c\u78ba\u4fdd\u8cc7\u6599\u985e\u578b\u7684\u517c\u5bb9\u6027\u3002\u901a\u904e\u4e86\u89e3 <code>DROP CAST<\/code> \u6307\u4ee4\u7684\u8a9e\u6cd5\u548c\u7528\u6cd5\uff0c\u7528\u6236\u53ef\u4ee5\u6709\u6548\u5730\u64cd\u4f5c\u5176 PostgreSQL \u8cc7\u6599\u5eab\u4e2d\u7684\u8f49\u63db\u3002<\/p>\n<h2 id=\"summary-PogQvDoenf\">\u7e3d\u7d50<\/h2>\n<p>\u7e3d\u7d50\u4f86\u8aaa\uff0cPostgreSQL \u4e2d\u7684 <code>DROP CAST<\/code> \u6307\u4ee4\u7528\u65bc\u79fb\u9664\u5169\u500b\u8cc7\u6599\u985e\u578b\u4e4b\u9593\u7684\u8f49\u63db\u3002\u5b83\u6709\u52a9\u65bc\u7ba1\u7406\u5132\u5b58\u5728\u7cfb\u7d71\u76ee\u9304\u4e2d\u7684\u8f49\u63db\u4fe1\u606f\u3002\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u53ef\u9760\u7684 VPS \u8a17\u7ba1\u89e3\u6c7a\u65b9\u6848\u4f86\u652f\u63f4\u60a8\u7684 PostgreSQL \u8cc7\u6599\u5eab\uff0c\u4e0d\u59a8\u8003\u616e <a href=\"https:\/\/server.hk\">Server.HK<\/a>\u3002Server.HK \u63d0\u4f9b\u9802\u7d1a\u7684 VPS \u89e3\u6c7a\u65b9\u6848\u548c\u512a\u79c0\u7684\u652f\u63f4\uff0c\u662f\u60a8\u8a17\u7ba1\u9700\u6c42\u7684\u7406\u60f3\u9078\u64c7\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>PostgreSQL \u6307\u4ee4\uff1aDR&#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-20759","post","type-post","status-publish","format-standard","hentry","category-setup-tutorials"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/20759","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=20759"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/20759\/revisions"}],"predecessor-version":[{"id":24353,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/20759\/revisions\/24353"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=20759"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=20759"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=20759"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}