{"id":79918,"date":"2024-10-16T13:43:16","date_gmt":"2024-10-16T05:43:16","guid":{"rendered":"https:\/\/server.hk\/cnblog\/79918\/"},"modified":"2024-10-16T13:43:16","modified_gmt":"2024-10-16T05:43:16","slug":"mysql%e6%8c%87%e4%bb%a4-substring%ef%bc%88%e5%ad%90%e4%b8%b2%ef%bc%89","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/79918\/","title":{"rendered":"MySQL\u6307\u4ee4: SUBSTRING()\uff08\u5b50\u4e32\uff09"},"content":{"rendered":"<h1 id=\"mysql%e6%8c%87%e4%bb%a4-substring%ef%bc%88%e5%ad%90%e4%b8%b2%ef%bc%89-qYFNPbwGxC\">MySQL\u6307\u4ee4: SUBSTRING()\uff08\u5b50\u4e32\uff09<\/h1>\n<p>\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0cMySQL\u662f\u4e00\u500b\u5ee3\u6cdb\u4f7f\u7528\u7684\u958b\u6e90\u95dc\u806f\u5f0f\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u3002\u5b83\u63d0\u4f9b\u4e86\u591a\u7a2e\u529f\u80fd\u5f37\u5927\u7684\u6307\u4ee4\u4f86\u8655\u7406\u548c\u64cd\u4f5c\u8cc7\u6599\u3002\u5176\u4e2d\uff0cSUBSTRING()\u51fd\u6578\u662f\u4e00\u500b\u975e\u5e38\u5be6\u7528\u7684\u5de5\u5177\uff0c\u80fd\u5920\u5f9e\u5b57\u4e32\u4e2d\u63d0\u53d6\u51fa\u7279\u5b9a\u7684\u5b50\u4e32\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0eSUBSTRING()\u51fd\u6578\u7684\u7528\u6cd5\u53ca\u5176\u61c9\u7528\u7bc4\u4f8b\u3002<\/p>\n<h2 id=\"substring%e5%87%bd%e6%95%b8%e6%a6%82%e8%bf%b0-qYFNPbwGxC\">SUBSTRING()\u51fd\u6578\u6982\u8ff0<\/h2>\n<p>SUBSTRING()\u51fd\u6578\u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>SUBSTRING(str, start, length)<\/code><\/pre>\n<ul>\n<li><strong>str<\/strong>: \u8981\u8655\u7406\u7684\u539f\u59cb\u5b57\u4e32\u3002<\/li>\n<li><strong>start<\/strong>: \u958b\u59cb\u63d0\u53d6\u7684\u8d77\u59cb\u4f4d\u7f6e\uff08\u5f9e1\u958b\u59cb\u8a08\u7b97\uff09\u3002<\/li>\n<li><strong>length<\/strong>: \u8981\u63d0\u53d6\u7684\u5b57\u5143\u6578\u91cf\uff08\u53ef\u9078\uff09\u3002<\/li>\n<\/ul>\n<p>\u5982\u679c\u4e0d\u6307\u5b9alength\uff0c\u5247SUBSTRING()\u5c07\u63d0\u53d6\u5f9estart\u4f4d\u7f6e\u5230\u5b57\u4e32\u7d50\u5c3e\u7684\u6240\u6709\u5b57\u5143\u3002<\/p>\n<h2 id=\"%e4%bd%bf%e7%94%a8%e7%af%84%e4%be%8b-qYFNPbwGxC\">\u4f7f\u7528\u7bc4\u4f8b<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e9b\u4f7f\u7528SUBSTRING()\u51fd\u6578\u7684\u7bc4\u4f8b\uff0c\u5e6b\u52a9\u8b80\u8005\u66f4\u597d\u5730\u7406\u89e3\u5176\u7528\u6cd5\u3002<\/p>\n<h3 id=\"%e7%af%84%e4%be%8b1-%e6%8f%90%e5%8f%96%e5%ad%97%e4%b8%b2%e7%9a%84%e4%b8%80%e9%83%a8%e5%88%86-qYFNPbwGxC\">\u7bc4\u4f8b1: \u63d0\u53d6\u5b57\u4e32\u7684\u4e00\u90e8\u5206<\/h3>\n<p>\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70bausers\u7684\u8cc7\u6599\u8868\uff0c\u88e1\u9762\u6709\u4e00\u500b\u540d\u70bausername\u7684\u6b04\u4f4d\uff0c\u5167\u5bb9\u5982\u4e0b\uff1a<\/p>\n<pre><code>username\n----------\njohn_doe\njane_smith\nalice_johnson\n<\/code><\/pre>\n<p>\u5982\u679c\u6211\u5011\u60f3\u63d0\u53d6\u6bcf\u500b\u4f7f\u7528\u8005\u540d\u7a31\u7684\u524d\u56db\u500b\u5b57\u5143\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0bSQL\u67e5\u8a62\uff1a<\/p>\n<pre><code>SELECT SUBSTRING(username, 1, 4) AS short_username FROM users;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de\uff1a<\/p>\n<pre><code>short_username\n---------------\njohn\njane\nalic\n<\/code><\/pre>\n<h3 id=\"%e7%af%84%e4%be%8b2-%e6%8f%90%e5%8f%96%e5%be%9e%e7%89%b9%e5%ae%9a%e4%bd%8d%e7%bd%ae%e9%96%8b%e5%a7%8b%e7%9a%84%e5%ad%97%e4%b8%b2-qYFNPbwGxC\">\u7bc4\u4f8b2: \u63d0\u53d6\u5f9e\u7279\u5b9a\u4f4d\u7f6e\u958b\u59cb\u7684\u5b57\u4e32<\/h3>\n<p>\u5982\u679c\u6211\u5011\u60f3\u5f9e\u6bcf\u500b\u4f7f\u7528\u8005\u540d\u7a31\u7684\u7b2c\u4e09\u500b\u5b57\u5143\u958b\u59cb\u63d0\u53d6\uff0c\u4e26\u63d0\u53d6\u5f8c\u9762\u7684\u6240\u6709\u5b57\u5143\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n<pre><code>SELECT SUBSTRING(username, 3) AS partial_username FROM users;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de\uff1a<\/p>\n<pre><code>partial_username\n-----------------\nhn_doe\nne_smith\nice_johnson\n<\/code><\/pre>\n<h3 id=\"%e7%af%84%e4%be%8b3-%e7%b5%90%e5%90%88%e5%85%b6%e4%bb%96%e5%87%bd%e6%95%b8%e4%bd%bf%e7%94%a8-qYFNPbwGxC\">\u7bc4\u4f8b3: \u7d50\u5408\u5176\u4ed6\u51fd\u6578\u4f7f\u7528<\/h3>\n<p>SUBSTRING()\u51fd\u6578\u4e5f\u53ef\u4ee5\u8207\u5176\u4ed6MySQL\u51fd\u6578\u7d50\u5408\u4f7f\u7528\u3002\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u60f3\u8981\u63d0\u53d6\u6bcf\u500b\u4f7f\u7528\u8005\u540d\u7a31\u7684\u6700\u5f8c\u4e09\u500b\u5b57\u5143\uff0c\u53ef\u4ee5\u4f7f\u7528LENGTH()\u51fd\u6578\u4f86\u8a08\u7b97\u5b57\u4e32\u7684\u9577\u5ea6\uff1a<\/p>\n<pre><code>SELECT SUBSTRING(username, LENGTH(username) - 2) AS last_three_chars FROM users;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de\uff1a<\/p>\n<pre><code>last_three_chars\n-----------------\n_doe\nith\nson\n<\/code><\/pre>\n<h2 id=\"%e6%b3%a8%e6%84%8f%e4%ba%8b%e9%a0%85-qYFNPbwGxC\">\u6ce8\u610f\u4e8b\u9805<\/h2>\n<p>\u5728\u4f7f\u7528SUBSTRING()\u51fd\u6578\u6642\uff0c\u6709\u5e7e\u9ede\u9700\u8981\u6ce8\u610f\uff1a<\/p>\n<ul>\n<li>\u8d77\u59cb\u4f4d\u7f6e\u662f\u5f9e1\u958b\u59cb\u8a08\u7b97\uff0c\u800c\u4e0d\u662f0\u3002<\/li>\n<li>\u5982\u679c\u8d77\u59cb\u4f4d\u7f6e\u8d85\u904e\u5b57\u4e32\u7684\u9577\u5ea6\uff0c\u5247\u8fd4\u56de\u7a7a\u5b57\u4e32\u3002<\/li>\n<li>\u5982\u679clength\u70ba\u8ca0\u6578\uff0c\u5247SUBSTRING()\u5c07\u8fd4\u56de\u7a7a\u5b57\u4e32\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b8%bd%e7%b5%90-qYFNPbwGxC\">\u7e3d\u7d50<\/h2>\n<p>SUBSTRING()\u51fd\u6578\u5728MySQL\u4e2d\u662f\u4e00\u500b\u975e\u5e38\u6709\u7528\u7684\u5de5\u5177\uff0c\u80fd\u5920\u5e6b\u52a9\u958b\u767c\u8005\u5f9e\u5b57\u4e32\u4e2d\u63d0\u53d6\u6240\u9700\u7684\u90e8\u5206\u3002\u7121\u8ad6\u662f\u5728\u8cc7\u6599\u67e5\u8a62\u9084\u662f\u8cc7\u6599\u8655\u7406\u4e2d\uff0c\u9019\u500b\u51fd\u6578\u90fd\u80fd\u63d0\u4f9b\u9748\u6d3b\u7684\u89e3\u6c7a\u65b9\u6848\u3002\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u8cc7\u6599\u8655\u7406\u7684\u61c9\u7528\uff0c\u9078\u64c7\u5408\u9069\u7684 <a href=\"https:\/\/server.hk\">VPS<\/a> \u65b9\u6848\u53ef\u4ee5\u9032\u4e00\u6b65\u63d0\u5347\u6027\u80fd\uff0c\u7279\u5225\u662f\u5728\u9999\u6e2f\u5730\u5340\uff0c<a href=\"https:\/\/server.hk\">\u9999\u6e2f\u4f3a\u670d\u5668<\/a> \u63d0\u4f9b\u4e86\u7a69\u5b9a\u7684\u652f\u6301\u3002\u5e0c\u671b\u672c\u6587\u80fd\u5e6b\u52a9\u60a8\u66f4\u597d\u5730\u7406\u89e3\u548c\u4f7f\u7528SUBSTRING()\u51fd\u6578\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3MySQL\u4e2d\u7684SUBSTRING()\u51fd\u6570\uff0c\u8f7b\u677e\u63d0\u53d6\u5b57\u7b26\u4e32\u4e2d\u7684\u5b50\u4e32\uff0c\u63d0\u5347\u6570\u636e\u5904\u7406\u6548\u7387\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-79918","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/79918","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=79918"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/79918\/revisions"}],"predecessor-version":[{"id":79919,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/79918\/revisions\/79919"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=79918"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=79918"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=79918"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}