{"id":179826,"date":"2024-11-09T05:07:16","date_gmt":"2024-11-08T21:07:16","guid":{"rendered":"https:\/\/server.hk\/cnblog\/179826\/"},"modified":"2024-11-09T05:07:17","modified_gmt":"2024-11-08T21:07:17","slug":"%e5%a6%82%e4%bd%95%e5%9c%a8%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%ad%e5%89%b5%e5%bb%ba%e9%bb%98%e8%aa%8d%e7%b4%84%e6%9d%9f%ef%bc%9f-%e6%95%b8%e6%93%9a%e5%ba%ab%e5%89%b5%e5%bb%ba-default-%e7%b4%84%e6%9d%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/179826\/","title":{"rendered":"\u5982\u4f55\u5728\u6578\u64da\u5eab\u4e2d\u5275\u5efa\u9ed8\u8a8d\u7d04\u675f\uff1f (\u6578\u64da\u5eab\u5275\u5efa default \u7d04\u675f)"},"content":{"rendered":"<h1 id=\"%e5%a6%82%e4%bd%95%e5%9c%a8%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%ad%e5%89%b5%e5%bb%ba%e9%bb%98%e8%aa%8d%e7%b4%84%e6%9d%9f%ef%bc%9f-%e6%95%b8%e6%93%9a%e5%ba%ab%e5%89%b5%e5%bb%ba-default-%e7%b4%84%e6%9d%9f-YhdVMLhJeS\">\u5982\u4f55\u5728\u6578\u64da\u5eab\u4e2d\u5275\u5efa\u9ed8\u8a8d\u7d04\u675f\uff1f (\u6578\u64da\u5eab\u5275\u5efa default \u7d04\u675f)<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u8a2d\u8a08\u4e2d\uff0c\u7d04\u675f\u662f\u7528\u4f86\u78ba\u4fdd\u6578\u64da\u7684\u5b8c\u6574\u6027\u548c\u6e96\u78ba\u6027\u7684\u91cd\u8981\u5de5\u5177\u3002\u5176\u4e2d\uff0c\u9ed8\u8a8d\u7d04\u675f\uff08Default Constraint\uff09\u662f\u4e00\u7a2e\u5e38\u7528\u7684\u7d04\u675f\u985e\u578b\uff0c\u4e3b\u8981\u7528\u65bc\u70ba\u6578\u64da\u8868\u4e2d\u7684\u67d0\u4e00\u5217\u6307\u5b9a\u4e00\u500b\u9ed8\u8a8d\u503c\uff0c\u7576\u63d2\u5165\u6578\u64da\u6642\u5982\u679c\u8a72\u5217\u672a\u63d0\u4f9b\u503c\uff0c\u5247\u81ea\u52d5\u4f7f\u7528\u9019\u500b\u9ed8\u8a8d\u503c\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5982\u4f55\u5728\u6578\u64da\u5eab\u4e2d\u5275\u5efa\u9ed8\u8a8d\u7d04\u675f\uff0c\u4e26\u63d0\u4f9b\u76f8\u95dc\u7684\u793a\u4f8b\u548c\u4ee3\u78bc\u7247\u6bb5\u3002<\/p>\n<h2 id=\"%e9%bb%98%e8%aa%8d%e7%b4%84%e6%9d%9f%e7%9a%84%e4%bd%9c%e7%94%a8-YhdVMLhJeS\">\u9ed8\u8a8d\u7d04\u675f\u7684\u4f5c\u7528<\/h2>\n<p>\u9ed8\u8a8d\u7d04\u675f\u7684\u4e3b\u8981\u4f5c\u7528\u662f\u7c21\u5316\u6578\u64da\u63d2\u5165\u64cd\u4f5c\uff0c\u6e1b\u5c11\u56e0\u70ba\u7f3a\u5c11\u6578\u64da\u800c\u5c0e\u81f4\u7684\u932f\u8aa4\u3002\u7576\u4e00\u500b\u5217\u88ab\u8a2d\u7f6e\u4e86\u9ed8\u8a8d\u7d04\u675f\u5f8c\uff0c\u958b\u767c\u8005\u5728\u63d2\u5165\u6578\u64da\u6642\u53ef\u4ee5\u9078\u64c7\u4e0d\u70ba\u8a72\u5217\u63d0\u4f9b\u503c\uff0c\u6578\u64da\u5eab\u7cfb\u7d71\u6703\u81ea\u52d5\u586b\u5145\u9ed8\u8a8d\u503c\u3002\u9019\u5728\u8655\u7406\u5927\u91cf\u6578\u64da\u6642\u7279\u5225\u6709\u7528\uff0c\u56e0\u70ba\u5b83\u53ef\u4ee5\u63d0\u9ad8\u6578\u64da\u63d2\u5165\u7684\u6548\u7387\u3002<\/p>\n<h2 id=\"%e5%89%b5%e5%bb%ba%e9%bb%98%e8%aa%8d%e7%b4%84%e6%9d%9f%e7%9a%84%e8%aa%9e%e6%b3%95-YhdVMLhJeS\">\u5275\u5efa\u9ed8\u8a8d\u7d04\u675f\u7684\u8a9e\u6cd5<\/h2>\n<p>\u5728 SQL \u4e2d\uff0c\u5275\u5efa\u9ed8\u8a8d\u7d04\u675f\u7684\u8a9e\u6cd5\u901a\u5e38\u5982\u4e0b\uff1a<\/p>\n<pre><code>CREATE TABLE \u8868\u540d (\n    \u5217\u540d \u6578\u64da\u985e\u578b DEFAULT \u9ed8\u8a8d\u503c,\n    ...\n);<\/code><\/pre>\n<p>\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u8981\u5275\u5efa\u4e00\u500b\u540d\u70ba <code>employees<\/code> \u7684\u8868\uff0c\u4e26\u70ba <code>salary<\/code> \u5217\u8a2d\u7f6e\u9ed8\u8a8d\u503c\u70ba 30000\uff0c\u5247\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b SQL \u8a9e\u53e5\uff1a<\/p>\n<pre><code>CREATE TABLE employees (\n    id INT PRIMARY KEY,\n    name VARCHAR(100),\n    salary DECIMAL(10, 2) DEFAULT 30000\n);<\/code><\/pre>\n<h2 id=\"%e5%9c%a8%e5%b7%b2%e5%ad%98%e5%9c%a8%e7%9a%84%e8%a1%a8%e4%b8%ad%e6%b7%bb%e5%8a%a0%e9%bb%98%e8%aa%8d%e7%b4%84%e6%9d%9f-YhdVMLhJeS\">\u5728\u5df2\u5b58\u5728\u7684\u8868\u4e2d\u6dfb\u52a0\u9ed8\u8a8d\u7d04\u675f<\/h2>\n<p>\u5982\u679c\u60a8\u5df2\u7d93\u6709\u4e00\u500b\u8868\u4e26\u5e0c\u671b\u70ba\u67d0\u4e00\u5217\u6dfb\u52a0\u9ed8\u8a8d\u7d04\u675f\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>ALTER TABLE<\/code> \u8a9e\u53e5\u3002\u4ee5\u4e0b\u662f\u6dfb\u52a0\u9ed8\u8a8d\u7d04\u675f\u7684\u8a9e\u6cd5\uff1a<\/p>\n<pre><code>ALTER TABLE \u8868\u540d\nADD CONSTRAINT \u7d04\u675f\u540d DEFAULT \u9ed8\u8a8d\u503c FOR \u5217\u540d;<\/code><\/pre>\n<p>\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u5df2\u7d93\u6709\u4e00\u500b\u540d\u70ba <code>employees<\/code> \u7684\u8868\uff0c\u4e26\u5e0c\u671b\u70ba <code>salary<\/code> \u5217\u6dfb\u52a0\u9ed8\u8a8d\u503c 30000\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b SQL \u8a9e\u53e5\uff1a<\/p>\n<pre><code>ALTER TABLE employees\nADD CONSTRAINT df_salary DEFAULT 30000 FOR salary;<\/code><\/pre>\n<h2 id=\"%e9%bb%98%e8%aa%8d%e7%b4%84%e6%9d%9f%e7%9a%84%e6%b3%a8%e6%84%8f%e4%ba%8b%e9%a0%85-YhdVMLhJeS\">\u9ed8\u8a8d\u7d04\u675f\u7684\u6ce8\u610f\u4e8b\u9805<\/h2>\n<ul>\n<li>\u9ed8\u8a8d\u7d04\u675f\u53ea\u80fd\u61c9\u7528\u65bc\u5217\u7684\u6578\u64da\u985e\u578b\u5fc5\u9808\u652f\u6301\u7684\u503c\u3002\u4f8b\u5982\uff0c\u5c0d\u65bc\u6574\u6578\u985e\u578b\u7684\u5217\uff0c\u9ed8\u8a8d\u503c\u5fc5\u9808\u662f\u6574\u6578\u3002<\/li>\n<li>\u5982\u679c\u5728\u63d2\u5165\u6578\u64da\u6642\u660e\u78ba\u6307\u5b9a\u4e86\u8a72\u5217\u7684\u503c\uff0c\u5247\u9ed8\u8a8d\u7d04\u675f\u4e0d\u6703\u751f\u6548\u3002<\/li>\n<li>\u5728\u67d0\u4e9b\u6578\u64da\u5eab\u7cfb\u7d71\u4e2d\uff0c\u9ed8\u8a8d\u7d04\u675f\u7684\u540d\u7a31\u662f\u53ef\u9078\u7684\uff0c\u4f46\u70ba\u4e86\u63d0\u9ad8\u53ef\u8b80\u6027\uff0c\u5efa\u8b70\u70ba\u7d04\u675f\u547d\u540d\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b5%90%e8%ab%96-YhdVMLhJeS\">\u7d50\u8ad6<\/h2>\n<p>\u9ed8\u8a8d\u7d04\u675f\u5728\u6578\u64da\u5eab\u8a2d\u8a08\u4e2d\u662f\u4e00\u500b\u975e\u5e38\u6709\u7528\u7684\u529f\u80fd\uff0c\u5b83\u80fd\u5920\u5e6b\u52a9\u958b\u767c\u8005\u7c21\u5316\u6578\u64da\u63d2\u5165\u64cd\u4f5c\uff0c\u4e26\u78ba\u4fdd\u6578\u64da\u7684\u5b8c\u6574\u6027\u3002\u901a\u904e\u672c\u6587\u7684\u4ecb\u7d39\uff0c\u60a8\u61c9\u8a72\u80fd\u5920\u7406\u89e3\u5982\u4f55\u5728\u6578\u64da\u5eab\u4e2d\u5275\u5efa\u548c\u7ba1\u7406\u9ed8\u8a8d\u7d04\u675f\u3002\u7121\u8ad6\u662f\u5728\u5275\u5efa\u65b0\u8868\u9084\u662f\u4fee\u6539\u73fe\u6709\u8868\uff0c\u6b63\u78ba\u4f7f\u7528\u9ed8\u8a8d\u7d04\u675f\u90fd\u80fd\u63d0\u9ad8\u6578\u64da\u5eab\u7684\u6548\u7387\u548c\u53ef\u9760\u6027\u3002<\/p>\n<p>\u5982\u679c\u60a8\u5c0d\u65bc\u6578\u64da\u5eab\u7ba1\u7406\u6216\u5176\u4ed6\u6280\u8853\u554f\u984c\u6709\u9032\u4e00\u6b65\u7684\u9700\u6c42\uff0c\u6b61\u8fce\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4e86\u89e3\u66f4\u591a\u8cc7\u8a0a\u3002\u6211\u5011\u63d0\u4f9b\u5404\u7a2e <a href=\"https:\/\/server.hk\">VPS<\/a> \u89e3\u6c7a\u65b9\u6848\uff0c\u5e6b\u52a9\u60a8\u5728\u9999\u6e2f\u7684\u696d\u52d9\u904b\u884c\u66f4\u52a0\u9806\u5229\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5b78\u7fd2\u5982\u4f55\u5728\u6578\u64da\u5eab\u4e2d\u5275\u5efa\u9ed8\u8a8d\u7d04\u675f\uff0c\u78ba\u4fdd\u5b57\u6bb5\u5728\u672a\u63d0\u4f9b\u503c\u6642\u81ea\u52d5\u586b\u5165\u9810\u8a2d\u503c\uff0c\u63d0\u9ad8\u6578\u64da\u5b8c\u6574\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-179826","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/179826","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=179826"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/179826\/revisions"}],"predecessor-version":[{"id":179827,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/179826\/revisions\/179827"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=179826"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=179826"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=179826"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}