{"id":179868,"date":"2024-11-09T05:28:18","date_gmt":"2024-11-08T21:28:18","guid":{"rendered":"https:\/\/server.hk\/cnblog\/179868\/"},"modified":"2024-11-09T05:28:19","modified_gmt":"2024-11-08T21:28:19","slug":"%e5%a6%82%e4%bd%95%e5%9c%a8%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%ad%e4%bd%bf%e7%94%a8-len-%e5%87%bd%e6%95%b8%ef%bc%9f-%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%ad-len-%e7%9a%84%e7%94%a8%e6%b3%95","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/179868\/","title":{"rendered":"\u5982\u4f55\u5728\u6578\u64da\u5eab\u4e2d\u4f7f\u7528 len \u51fd\u6578\uff1f (\u6578\u64da\u5eab\u4e2d len \u7684\u7528\u6cd5)"},"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%e4%bd%bf%e7%94%a8-len-%e5%87%bd%e6%95%b8%ef%bc%9f-%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%ad-len-%e7%9a%84%e7%94%a8%e6%b3%95-URqNZqRSyf\">\u5982\u4f55\u5728\u6578\u64da\u5eab\u4e2d\u4f7f\u7528 len \u51fd\u6578\uff1f (\u6578\u64da\u5eab\u4e2d len \u7684\u7528\u6cd5)<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0c<code>len<\/code> \u51fd\u6578\u662f\u4e00\u500b\u975e\u5e38\u6709\u7528\u7684\u5de5\u5177\uff0c\u4e3b\u8981\u7528\u65bc\u8a08\u7b97\u5b57\u7b26\u4e32\u7684\u9577\u5ea6\u3002\u7121\u8ad6\u662f\u5728\u6578\u64da\u6e05\u7406\u3001\u6578\u64da\u5206\u6790\u9084\u662f\u6578\u64da\u5831\u544a\u4e2d\uff0c\u4e86\u89e3\u5982\u4f55\u6b63\u78ba\u4f7f\u7528 <code>len<\/code> \u51fd\u6578\u90fd\u80fd\u5e6b\u52a9\u958b\u767c\u8005\u548c\u6578\u64da\u5206\u6790\u5e2b\u66f4\u6709\u6548\u5730\u8655\u7406\u6578\u64da\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e <code>len<\/code> \u51fd\u6578\u7684\u7528\u6cd5\u53ca\u5176\u5728\u4e0d\u540c\u6578\u64da\u5eab\u7cfb\u7d71\u4e2d\u7684\u61c9\u7528\u3002<\/p>\n<h2 id=\"len-%e5%87%bd%e6%95%b8%e7%9a%84%e5%9f%ba%e6%9c%ac%e6%a6%82%e5%bf%b5-URqNZqRSyf\">len \u51fd\u6578\u7684\u57fa\u672c\u6982\u5ff5<\/h2>\n<p><code>len<\/code> \u51fd\u6578\u7684\u4e3b\u8981\u529f\u80fd\u662f\u8fd4\u56de\u4e00\u500b\u5b57\u7b26\u4e32\u7684\u5b57\u7b26\u6578\u3002\u9019\u5728\u8655\u7406\u6587\u672c\u6578\u64da\u6642\u7279\u5225\u91cd\u8981\uff0c\u56e0\u70ba\u5b83\u53ef\u4ee5\u5e6b\u52a9\u6211\u5011\u4e86\u89e3\u6578\u64da\u7684\u7d50\u69cb\u548c\u5167\u5bb9\u3002\u4e0d\u540c\u7684\u6578\u64da\u5eab\u7cfb\u7d71\u5c0d <code>len<\/code> \u51fd\u6578\u7684\u5be6\u73fe\u53ef\u80fd\u7565\u6709\u4e0d\u540c\uff0c\u4f46\u5176\u57fa\u672c\u539f\u7406\u662f\u4e00\u81f4\u7684\u3002<\/p>\n<h2 id=\"%e5%9c%a8%e4%b8%8d%e5%90%8c%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%ad%e7%9a%84-len-%e5%87%bd%e6%95%b8%e7%94%a8%e6%b3%95-URqNZqRSyf\">\u5728\u4e0d\u540c\u6578\u64da\u5eab\u4e2d\u7684 len \u51fd\u6578\u7528\u6cd5<\/h2>\n<h3 id=\"1-sql-server-URqNZqRSyf\">1. SQL Server<\/h3>\n<p>\u5728 SQL Server \u4e2d\uff0c\u4f7f\u7528 <code>LEN<\/code> \u51fd\u6578\u4f86\u8a08\u7b97\u5b57\u7b26\u4e32\u7684\u9577\u5ea6\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u793a\u4f8b\uff1a<\/p>\n<pre><code>SELECT LEN('Hello, World!') AS StringLength;<\/code><\/pre>\n<p>\u9019\u6bb5\u4ee3\u78bc\u5c07\u8fd4\u56de\u5b57\u7b26\u4e32 &#8220;Hello, World!&#8221; \u7684\u9577\u5ea6\uff0c\u5373 13\u3002<\/p>\n<h3 id=\"2-mysql-URqNZqRSyf\">2. MySQL<\/h3>\n<p>\u5728 MySQL \u4e2d\uff0c\u4f7f\u7528 <code>CHAR_LENGTH<\/code> \u6216 <code>LENGTH<\/code> \u51fd\u6578\u4f86\u7372\u53d6\u5b57\u7b26\u4e32\u7684\u9577\u5ea6\u3002<code>CHAR_LENGTH<\/code> \u8fd4\u56de\u5b57\u7b26\u6578\uff0c\u800c <code>LENGTH<\/code> \u8fd4\u56de\u5b57\u7bc0\u6578\u3002\u4ee5\u4e0b\u662f\u793a\u4f8b\uff1a<\/p>\n<pre><code>SELECT CHAR_LENGTH('Hello, World!') AS StringLength;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de 13\uff0c\u800c\u4f7f\u7528 <code>LENGTH<\/code> \u51fd\u6578\u5247\u53ef\u80fd\u6839\u64da\u5b57\u7b26\u96c6\u7684\u4e0d\u540c\u800c\u6709\u6240\u4e0d\u540c\u3002<\/p>\n<h3 id=\"3-postgresql-URqNZqRSyf\">3. PostgreSQL<\/h3>\n<p>\u5728 PostgreSQL \u4e2d\uff0c<code>LENGTH<\/code> \u51fd\u6578\u7528\u65bc\u8a08\u7b97\u5b57\u7b26\u4e32\u7684\u9577\u5ea6\u3002\u793a\u4f8b\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT LENGTH('Hello, World!') AS StringLength;<\/code><\/pre>\n<p>\u9019\u540c\u6a23\u6703\u8fd4\u56de 13\u3002<\/p>\n<h3 id=\"4-oracle-URqNZqRSyf\">4. Oracle<\/h3>\n<p>\u5728 Oracle \u6578\u64da\u5eab\u4e2d\uff0c\u4f7f\u7528 <code>LENGTH<\/code> \u51fd\u6578\u4f86\u8a08\u7b97\u5b57\u7b26\u4e32\u7684\u9577\u5ea6\u3002\u4ee5\u4e0b\u662f\u793a\u4f8b\uff1a<\/p>\n<pre><code>SELECT LENGTH('Hello, World!') AS StringLength FROM dual;<\/code><\/pre>\n<p>\u9019\u6bb5\u4ee3\u78bc\u4e5f\u6703\u8fd4\u56de 13\u3002<\/p>\n<h2 id=\"len-%e5%87%bd%e6%95%b8%e7%9a%84%e5%af%a6%e9%9a%9b%e6%87%89%e7%94%a8-URqNZqRSyf\">len \u51fd\u6578\u7684\u5be6\u969b\u61c9\u7528<\/h2>\n<p>\u5728\u5be6\u969b\u61c9\u7528\u4e2d\uff0c<code>len<\/code> \u51fd\u6578\u53ef\u4ee5\u7528\u65bc\u591a\u7a2e\u5834\u666f\uff0c\u4f8b\u5982\uff1a<\/p>\n<ul>\n<li><strong>\u6578\u64da\u9a57\u8b49\uff1a<\/strong>\u5728\u63d2\u5165\u6578\u64da\u4e4b\u524d\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>len<\/code> \u51fd\u6578\u6aa2\u67e5\u5b57\u7b26\u4e32\u7684\u9577\u5ea6\uff0c\u4ee5\u78ba\u4fdd\u5176\u7b26\u5408\u9810\u671f\u7684\u683c\u5f0f\u3002<\/li>\n<li><strong>\u6578\u64da\u6e05\u7406\uff1a<\/strong>\u5728\u6578\u64da\u6e05\u7406\u904e\u7a0b\u4e2d\uff0c\u53ef\u4ee5\u904e\u6ffe\u6389\u9577\u5ea6\u4e0d\u7b26\u5408\u8981\u6c42\u7684\u6578\u64da\u3002<\/li>\n<li><strong>\u5831\u544a\u751f\u6210\uff1a<\/strong>\u5728\u751f\u6210\u5831\u544a\u6642\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>len<\/code> \u51fd\u6578\u4f86\u8a08\u7b97\u5b57\u6bb5\u7684\u9577\u5ea6\uff0c\u5f9e\u800c\u63d0\u4f9b\u66f4\u8a73\u7d30\u7684\u6578\u64da\u5206\u6790\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b5%90%e8%ab%96-URqNZqRSyf\">\u7d50\u8ad6<\/h2>\n<p>\u7e3d\u7d50\u4f86\u8aaa\uff0c<code>len<\/code> \u51fd\u6578\u5728\u6578\u64da\u5eab\u4e2d\u662f\u4e00\u500b\u975e\u5e38\u91cd\u8981\u7684\u5de5\u5177\uff0c\u80fd\u5920\u5e6b\u52a9\u7528\u6236\u6709\u6548\u5730\u8655\u7406\u548c\u5206\u6790\u5b57\u7b26\u4e32\u6578\u64da\u3002\u7121\u8ad6\u662f\u5728 SQL Server\u3001MySQL\u3001PostgreSQL \u9084\u662f Oracle \u4e2d\uff0c\u638c\u63e1 <code>len<\/code> \u51fd\u6578\u7684\u7528\u6cd5\u90fd\u80fd\u63d0\u5347\u6578\u64da\u8655\u7406\u7684\u6548\u7387\u548c\u6e96\u78ba\u6027\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684 <a href=\"https:\/\/server.hk\">VPS<\/a> \u89e3\u6c7a\u65b9\u6848\uff0cServer.HK \u63d0\u4f9b\u591a\u7a2e\u9078\u64c7\uff0c\u6eff\u8db3\u60a8\u7684\u9700\u6c42\u3002\u7121\u8ad6\u662f <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u9084\u662f\u5176\u4ed6\u670d\u52d9\uff0c\u6211\u5011\u90fd\u80fd\u70ba\u60a8\u63d0\u4f9b\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3\u5982\u4f55\u5728\u6578\u64da\u5eab\u4e2d\u4f7f\u7528 len \u51fd\u6578\u4f86\u8a08\u7b97\u5b57\u7b26\u4e32\u9577\u5ea6\uff0c\u63d0\u5347\u6578\u64da\u8655\u7406\u6548\u7387\uff0c\u7c21\u5316\u67e5\u8a62\u64cd\u4f5c\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-179868","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/179868","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=179868"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/179868\/revisions"}],"predecessor-version":[{"id":179869,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/179868\/revisions\/179869"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=179868"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=179868"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=179868"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}