{"id":168383,"date":"2024-11-06T11:55:28","date_gmt":"2024-11-06T03:55:28","guid":{"rendered":"https:\/\/server.hk\/cnblog\/168383\/"},"modified":"2024-11-06T11:55:28","modified_gmt":"2024-11-06T03:55:28","slug":"sql-%e6%95%b8%e6%93%9a%e5%ba%ab%e5%ad%97%e6%ae%b5%e9%95%b7%e5%ba%a6%e8%aa%bf%e6%95%b4%e6%8a%80%e5%b7%a7-%e5%b0%8d-sql-%e6%95%b8%e6%93%9a%e5%ba%ab%e5%ad%97%e6%ae%b5%e9%95%b7%e5%ba%a6%e4%bf%ae%e6%94%b9","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/168383\/","title":{"rendered":"SQL \u6578\u64da\u5eab\u5b57\u6bb5\u9577\u5ea6\u8abf\u6574\u6280\u5de7 (\u5c0d sql \u6578\u64da\u5eab\u5b57\u6bb5\u9577\u5ea6\u4fee\u6539)"},"content":{"rendered":"<h1 id=\"sql-%e6%95%b8%e6%93%9a%e5%ba%ab%e5%ad%97%e6%ae%b5%e9%95%b7%e5%ba%a6%e8%aa%bf%e6%95%b4%e6%8a%80%e5%b7%a7-%e5%b0%8d-sql-%e6%95%b8%e6%93%9a%e5%ba%ab%e5%ad%97%e6%ae%b5%e9%95%b7%e5%ba%a6%e4%bf%ae%e6%94%b9-xvcByKZbFJ\">SQL \u6578\u64da\u5eab\u5b57\u6bb5\u9577\u5ea6\u8abf\u6574\u6280\u5de7 (\u5c0d SQL \u6578\u64da\u5eab\u5b57\u6bb5\u9577\u5ea6\u4fee\u6539)<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u8a2d\u8a08\u4e2d\uff0c\u5b57\u6bb5\u7684\u9577\u5ea6\u8a2d\u5b9a\u5c0d\u65bc\u6578\u64da\u7684\u5b58\u5132\u548c\u67e5\u8a62\u6027\u80fd\u6709\u8457\u91cd\u8981\u5f71\u97ff\u3002\u96a8\u8457\u696d\u52d9\u9700\u6c42\u7684\u8b8a\u5316\uff0c\u53ef\u80fd\u9700\u8981\u5c0d\u73fe\u6709\u5b57\u6bb5\u7684\u9577\u5ea6\u9032\u884c\u8abf\u6574\u3002\u672c\u6587\u5c07\u63a2\u8a0e SQL \u6578\u64da\u5eab\u5b57\u6bb5\u9577\u5ea6\u8abf\u6574\u7684\u6280\u5de7\uff0c\u5e6b\u52a9\u958b\u767c\u8005\u66f4\u6709\u6548\u5730\u7ba1\u7406\u6578\u64da\u5eab\u7d50\u69cb\u3002<\/p>\n<h2 id=\"%e7%82%ba%e4%bb%80%e9%ba%bc%e9%9c%80%e8%a6%81%e8%aa%bf%e6%95%b4%e5%ad%97%e6%ae%b5%e9%95%b7%e5%ba%a6-xvcByKZbFJ\">\u70ba\u4ec0\u9ebc\u9700\u8981\u8abf\u6574\u5b57\u6bb5\u9577\u5ea6<\/h2>\n<p>\u8abf\u6574\u5b57\u6bb5\u9577\u5ea6\u7684\u539f\u56e0\u591a\u7a2e\u591a\u6a23\uff0c\u5305\u62ec\uff1a<\/p>\n<ul>\n<li><strong>\u6578\u64da\u9700\u6c42\u8b8a\u66f4\uff1a<\/strong>\u96a8\u8457\u696d\u52d9\u7684\u767c\u5c55\uff0c\u539f\u6709\u7684\u5b57\u6bb5\u9577\u5ea6\u53ef\u80fd\u7121\u6cd5\u6eff\u8db3\u65b0\u7684\u6578\u64da\u9700\u6c42\u3002<\/li>\n<li><strong>\u6027\u80fd\u512a\u5316\uff1a<\/strong>\u904e\u9577\u7684\u5b57\u6bb5\u53ef\u80fd\u5c0e\u81f4\u5b58\u5132\u7a7a\u9593\u6d6a\u8cbb\uff0c\u5f71\u97ff\u67e5\u8a62\u6027\u80fd\u3002<\/li>\n<li><strong>\u6578\u64da\u4e00\u81f4\u6027\uff1a<\/strong>\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u53ef\u80fd\u9700\u8981\u7d71\u4e00\u5b57\u6bb5\u9577\u5ea6\u4ee5\u4fdd\u6301\u6578\u64da\u7684\u4e00\u81f4\u6027\u3002<\/li>\n<\/ul>\n<h2 id=\"%e8%aa%bf%e6%95%b4%e5%ad%97%e6%ae%b5%e9%95%b7%e5%ba%a6%e7%9a%84%e5%9f%ba%e6%9c%ac%e6%ad%a5%e9%a9%9f-xvcByKZbFJ\">\u8abf\u6574\u5b57\u6bb5\u9577\u5ea6\u7684\u57fa\u672c\u6b65\u9a5f<\/h2>\n<p>\u5728 SQL \u6578\u64da\u5eab\u4e2d\uff0c\u8abf\u6574\u5b57\u6bb5\u9577\u5ea6\u901a\u5e38\u6d89\u53ca\u4ee5\u4e0b\u5e7e\u500b\u6b65\u9a5f\uff1a<\/p>\n<h3 id=\"1-%e7%a2%ba%e8%aa%8d%e7%95%b6%e5%89%8d%e5%ad%97%e6%ae%b5%e9%95%b7%e5%ba%a6-xvcByKZbFJ\">1. \u78ba\u8a8d\u7576\u524d\u5b57\u6bb5\u9577\u5ea6<\/h3>\n<p>\u9996\u5148\uff0c\u4f7f\u7528\u4ee5\u4e0b SQL \u67e5\u8a62\u4f86\u6aa2\u67e5\u7576\u524d\u5b57\u6bb5\u7684\u9577\u5ea6\uff1a<\/p>\n<pre><code>SELECT COLUMN_NAME, CHARACTER_MAXIMUM_LENGTH \nFROM INFORMATION_SCHEMA.COLUMNS \nWHERE TABLE_NAME = 'your_table_name';<\/code><\/pre>\n<h3 id=\"2-%e8%a9%95%e4%bc%b0%e6%96%b0%e9%95%b7%e5%ba%a6-xvcByKZbFJ\">2. \u8a55\u4f30\u65b0\u9577\u5ea6<\/h3>\n<p>\u5728\u6c7a\u5b9a\u65b0\u9577\u5ea6\u4e4b\u524d\uff0c\u61c9\u8a72\u8a55\u4f30\u6578\u64da\u7684\u5be6\u969b\u9700\u6c42\u3002\u4f8b\u5982\uff0c\u5982\u679c\u4e00\u500b\u7528\u65bc\u5b58\u5132\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\u7684\u5b57\u6bb5\u539f\u672c\u8a2d\u7f6e\u70ba 50 \u500b\u5b57\u7b26\uff0c\u7d93\u904e\u5206\u6790\u5f8c\u767c\u73fe\u5927\u591a\u6578\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\u90fd\u5728 30 \u500b\u5b57\u7b26\u4ee5\u5167\uff0c\u90a3\u9ebc\u53ef\u4ee5\u8003\u616e\u5c07\u5176\u8abf\u6574\u70ba 40 \u500b\u5b57\u7b26\u3002<\/p>\n<h3 id=\"3-%e4%bf%ae%e6%94%b9%e5%ad%97%e6%ae%b5%e9%95%b7%e5%ba%a6-xvcByKZbFJ\">3. \u4fee\u6539\u5b57\u6bb5\u9577\u5ea6<\/h3>\n<p>\u4f7f\u7528 ALTER TABLE \u8a9e\u53e5\u4f86\u4fee\u6539\u5b57\u6bb5\u9577\u5ea6\u3002\u4ee5\u4e0b\u662f\u4fee\u6539\u5b57\u6bb5\u9577\u5ea6\u7684\u57fa\u672c\u8a9e\u6cd5\uff1a<\/p>\n<pre><code>ALTER TABLE your_table_name \nMODIFY COLUMN your_column_name VARCHAR(new_length);<\/code><\/pre>\n<p>\u4f8b\u5982\uff0c\u5c07 &#8217;email&#8217; \u5b57\u6bb5\u7684\u9577\u5ea6\u5f9e 50 \u8abf\u6574\u70ba 40\uff1a<\/p>\n<pre><code>ALTER TABLE users \nMODIFY COLUMN email VARCHAR(40);<\/code><\/pre>\n<h3 id=\"4-%e6%b8%ac%e8%a9%a6%e5%92%8c%e9%a9%97%e8%ad%89-xvcByKZbFJ\">4. \u6e2c\u8a66\u548c\u9a57\u8b49<\/h3>\n<p>\u5728\u4fee\u6539\u5b57\u6bb5\u9577\u5ea6\u5f8c\uff0c\u61c9\u8a72\u9032\u884c\u6e2c\u8a66\u4ee5\u78ba\u4fdd\u6578\u64da\u7684\u5b8c\u6574\u6027\u548c\u61c9\u7528\u7a0b\u5e8f\u7684\u6b63\u5e38\u904b\u884c\u3002\u53ef\u4ee5\u901a\u904e\u63d2\u5165\u3001\u66f4\u65b0\u548c\u67e5\u8a62\u6578\u64da\u4f86\u9a57\u8b49\u4fee\u6539\u662f\u5426\u6210\u529f\u3002<\/p>\n<h2 id=\"%e6%b3%a8%e6%84%8f%e4%ba%8b%e9%a0%85-xvcByKZbFJ\">\u6ce8\u610f\u4e8b\u9805<\/h2>\n<p>\u5728\u8abf\u6574\u5b57\u6bb5\u9577\u5ea6\u6642\uff0c\u9700\u8981\u6ce8\u610f\u4ee5\u4e0b\u5e7e\u9ede\uff1a<\/p>\n<ul>\n<li><strong>\u6578\u64da\u4e1f\u5931\u98a8\u96aa\uff1a<\/strong>\u5982\u679c\u5c07\u5b57\u6bb5\u9577\u5ea6\u7e2e\u77ed\uff0c\u53ef\u80fd\u6703\u5c0e\u81f4\u73fe\u6709\u6578\u64da\u88ab\u622a\u65b7\uff0c\u56e0\u6b64\u5728\u9032\u884c\u6b64\u64cd\u4f5c\u4e4b\u524d\uff0c\u5efa\u8b70\u5099\u4efd\u6578\u64da\u3002<\/li>\n<li><strong>\u5f71\u97ff\u6027\u80fd\uff1a<\/strong>\u4fee\u6539\u5b57\u6bb5\u9577\u5ea6\u53ef\u80fd\u6703\u5f71\u97ff\u6578\u64da\u5eab\u7684\u6027\u80fd\uff0c\u7279\u5225\u662f\u5728\u5927\u578b\u6578\u64da\u8868\u4e2d\uff0c\u56e0\u6b64\u61c9\u5728\u4f4e\u5cf0\u671f\u9032\u884c\u64cd\u4f5c\u3002<\/li>\n<li><strong>\u61c9\u7528\u7a0b\u5e8f\u517c\u5bb9\u6027\uff1a<\/strong>\u78ba\u4fdd\u61c9\u7528\u7a0b\u5e8f\u4e2d\u7684\u4ee3\u78bc\u80fd\u5920\u6b63\u78ba\u8655\u7406\u65b0\u7684\u5b57\u6bb5\u9577\u5ea6\uff0c\u907f\u514d\u51fa\u73fe\u932f\u8aa4\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b5%90%e8%ab%96-xvcByKZbFJ\">\u7d50\u8ad6<\/h2>\n<p>\u8abf\u6574 SQL \u6578\u64da\u5eab\u5b57\u6bb5\u9577\u5ea6\u662f\u4e00\u9805\u91cd\u8981\u7684\u7dad\u8b77\u4efb\u52d9\uff0c\u80fd\u5920\u5e6b\u52a9\u958b\u767c\u8005\u66f4\u597d\u5730\u7ba1\u7406\u6578\u64da\u7d50\u69cb\u3002\u901a\u904e\u9075\u5faa\u4e0a\u8ff0\u6b65\u9a5f\u548c\u6ce8\u610f\u4e8b\u9805\uff0c\u53ef\u4ee5\u6709\u6548\u5730\u9032\u884c\u5b57\u6bb5\u9577\u5ea6\u7684\u4fee\u6539\uff0c\u5f9e\u800c\u63d0\u5347\u6578\u64da\u5eab\u7684\u6027\u80fd\u548c\u9748\u6d3b\u6027\u3002<\/p>\n<p>\u5982\u9700\u4e86\u89e3\u66f4\u591a\u6709\u95dc <a href=\"https:\/\/server.hk\">VPS<\/a> \u548c\u6578\u64da\u5eab\u7ba1\u7406\u7684\u8cc7\u8a0a\uff0c\u8acb\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u638c\u63e1SQL\u6578\u64da\u5eab\u5b57\u6bb5\u9577\u5ea6\u8abf\u6574\u6280\u5de7\uff0c\u8f15\u9b06\u4fee\u6539\u5b57\u6bb5\u9577\u5ea6\uff0c\u63d0\u5347\u6578\u64da\u7ba1\u7406\u6548\u7387\uff0c\u78ba\u4fdd\u6578\u64da\u5b8c\u6574\u6027\u8207\u6027\u80fd\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-168383","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168383","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=168383"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168383\/revisions"}],"predecessor-version":[{"id":168384,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168383\/revisions\/168384"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=168383"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=168383"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=168383"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}