{"id":179432,"date":"2024-11-09T01:46:17","date_gmt":"2024-11-08T17:46:17","guid":{"rendered":"https:\/\/server.hk\/cnblog\/179432\/"},"modified":"2024-11-09T01:46:18","modified_gmt":"2024-11-08T17:46:18","slug":"%e5%a6%82%e4%bd%95%e5%84%aa%e5%8c%96%e6%95%b8%e6%93%9a%e5%ba%ab%e5%ad%97%e7%ac%a6%e9%95%b7%e5%ba%a6%ef%bc%9f-%e6%95%b8%e6%93%9a%e5%ba%ab-%e5%ad%97%e7%ac%a6%e9%95%b7%e5%ba%a6","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/179432\/","title":{"rendered":"\u5982\u4f55\u512a\u5316\u6578\u64da\u5eab\u5b57\u7b26\u9577\u5ea6\uff1f (\u6578\u64da\u5eab \u5b57\u7b26\u9577\u5ea6)"},"content":{"rendered":"<h1 id=\"%e5%a6%82%e4%bd%95%e5%84%aa%e5%8c%96%e6%95%b8%e6%93%9a%e5%ba%ab%e5%ad%97%e7%ac%a6%e9%95%b7%e5%ba%a6%ef%bc%9f-VnizfYaqjY\">\u5982\u4f55\u512a\u5316\u6578\u64da\u5eab\u5b57\u7b26\u9577\u5ea6\uff1f<\/h1>\n<p>\u5728\u7576\u4eca\u6578\u64da\u9a45\u52d5\u7684\u4e16\u754c\u4e2d\uff0c\u6578\u64da\u5eab\u7684\u6027\u80fd\u548c\u6548\u7387\u5c0d\u65bc\u61c9\u7528\u7a0b\u5e8f\u7684\u6210\u529f\u81f3\u95dc\u91cd\u8981\u3002\u5b57\u7b26\u9577\u5ea6\u7684\u512a\u5316\u662f\u6578\u64da\u5eab\u8a2d\u8a08\u4e2d\u7684\u4e00\u500b\u91cd\u8981\u65b9\u9762\uff0c\u80fd\u5920\u986f\u8457\u5f71\u97ff\u6578\u64da\u5eab\u7684\u5b58\u5132\u6548\u7387\u548c\u67e5\u8a62\u6027\u80fd\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5982\u4f55\u6709\u6548\u5730\u512a\u5316\u6578\u64da\u5eab\u4e2d\u7684\u5b57\u7b26\u9577\u5ea6\u3002<\/p>\n<h2 id=\"%e7%90%86%e8%a7%a3%e5%ad%97%e7%ac%a6%e9%95%b7%e5%ba%a6%e7%9a%84%e9%87%8d%e8%a6%81%e6%80%a7-VnizfYaqjY\">\u7406\u89e3\u5b57\u7b26\u9577\u5ea6\u7684\u91cd\u8981\u6027<\/h2>\n<p>\u5b57\u7b26\u9577\u5ea6\u6307\u7684\u662f\u5728\u6578\u64da\u5eab\u4e2d\u5b58\u5132\u5b57\u7b26\u4e32\u6578\u64da\u6240\u9700\u7684\u7a7a\u9593\u3002\u4e0d\u540c\u7684\u6578\u64da\u5eab\u7cfb\u7d71\u5c0d\u5b57\u7b26\u9577\u5ea6\u7684\u8655\u7406\u65b9\u5f0f\u53ef\u80fd\u6709\u6240\u4e0d\u540c\uff0c\u4f46\u4e00\u822c\u4f86\u8aaa\uff0c\u5b57\u7b26\u9577\u5ea6\u7684\u9078\u64c7\u6703\u5f71\u97ff\u4ee5\u4e0b\u5e7e\u500b\u65b9\u9762\uff1a<\/p>\n<ul>\n<li><strong>\u5b58\u5132\u7a7a\u9593\uff1a<\/strong>\u904e\u9577\u7684\u5b57\u7b26\u5b57\u6bb5\u6703\u6d6a\u8cbb\u5b58\u5132\u7a7a\u9593\uff0c\u589e\u52a0\u6578\u64da\u5eab\u7684\u5927\u5c0f\u3002<\/li>\n<li><strong>\u67e5\u8a62\u6027\u80fd\uff1a<\/strong>\u67e5\u8a62\u904e\u9577\u7684\u5b57\u7b26\u4e32\u53ef\u80fd\u6703\u5c0e\u81f4\u6027\u80fd\u4e0b\u964d\uff0c\u7279\u5225\u662f\u5728\u9032\u884c\u7d22\u5f15\u6642\u3002<\/li>\n<li><strong>\u6578\u64da\u5b8c\u6574\u6027\uff1a<\/strong>\u4e0d\u5408\u7406\u7684\u5b57\u7b26\u9577\u5ea6\u53ef\u80fd\u5c0e\u81f4\u6578\u64da\u622a\u65b7\u6216\u932f\u8aa4\u3002<\/li>\n<\/ul>\n<h2 id=\"%e9%81%b8%e6%93%87%e5%90%88%e9%81%a9%e7%9a%84%e6%95%b8%e6%93%9a%e9%a1%9e%e5%9e%8b-VnizfYaqjY\">\u9078\u64c7\u5408\u9069\u7684\u6578\u64da\u985e\u578b<\/h2>\n<p>\u5728\u8a2d\u8a08\u6578\u64da\u5eab\u6642\uff0c\u9078\u64c7\u5408\u9069\u7684\u6578\u64da\u985e\u578b\u662f\u512a\u5316\u5b57\u7b26\u9577\u5ea6\u7684\u7b2c\u4e00\u6b65\u3002\u5e38\u898b\u7684\u5b57\u7b26\u6578\u64da\u985e\u578b\u5305\u62ec\uff1a<\/p>\n<ul>\n<li><strong>CHAR(n)\uff1a<\/strong>\u56fa\u5b9a\u9577\u5ea6\u7684\u5b57\u7b26\u4e32\uff0c\u9069\u5408\u5b58\u5132\u9577\u5ea6\u4e00\u81f4\u7684\u6578\u64da\u3002<\/li>\n<li><strong>VARCHAR(n)\uff1a<\/strong>\u53ef\u8b8a\u9577\u5ea6\u7684\u5b57\u7b26\u4e32\uff0c\u9069\u5408\u5b58\u5132\u9577\u5ea6\u4e0d\u4e00\u7684\u6578\u64da\u3002<\/li>\n<li><strong>TEXT\uff1a<\/strong>\u7528\u65bc\u5b58\u5132\u9577\u6587\u672c\uff0c\u9069\u5408\u5b58\u5132\u5927\u91cf\u6587\u672c\u6578\u64da\u3002<\/li>\n<\/ul>\n<p>\u4f8b\u5982\uff0c\u5982\u679c\u60a8\u77e5\u9053\u67d0\u500b\u5b57\u6bb5\u7684\u6578\u64da\u9577\u5ea6\u4e0d\u6703\u8d85\u904e50\u500b\u5b57\u7b26\uff0c\u5247\u4f7f\u7528VARCHAR(50)\u6703\u6bd4\u4f7f\u7528VARCHAR(255)\u66f4\u6709\u6548\uff0c\u56e0\u70ba\u5b83\u80fd\u5920\u7bc0\u7701\u5b58\u5132\u7a7a\u9593\u3002<\/p>\n<h2 id=\"%e5%88%86%e6%9e%90%e6%95%b8%e6%93%9a%e9%9c%80%e6%b1%82-VnizfYaqjY\">\u5206\u6790\u6578\u64da\u9700\u6c42<\/h2>\n<p>\u5728\u8a2d\u8a08\u6578\u64da\u5eab\u6642\uff0c\u4e86\u89e3\u6578\u64da\u7684\u5be6\u969b\u9700\u6c42\u662f\u81f3\u95dc\u91cd\u8981\u7684\u3002\u901a\u904e\u5206\u6790\u73fe\u6709\u6578\u64da\uff0c\u53ef\u4ee5\u66f4\u597d\u5730\u6c7a\u5b9a\u5b57\u7b26\u9577\u5ea6\u3002\u4f8b\u5982\uff0c\u5c0d\u65bc\u7528\u6236\u540d\u5b57\u6bb5\uff0c\u60a8\u53ef\u4ee5\u67e5\u770b\u73fe\u6709\u7528\u6236\u540d\u7684\u9577\u5ea6\u5206\u4f48\uff0c\u4e26\u6839\u64da\u5be6\u969b\u60c5\u6cc1\u9078\u64c7\u5408\u9069\u7684\u9577\u5ea6\u3002<\/p>\n<pre><code>SELECT LENGTH(username) AS length, COUNT(*) AS count\nFROM users\nGROUP BY length\nORDER BY length;<\/code><\/pre>\n<p>\u9019\u6bb5SQL\u67e5\u8a62\u53ef\u4ee5\u5e6b\u52a9\u60a8\u4e86\u89e3\u7528\u6236\u540d\u7684\u9577\u5ea6\u5206\u4f48\uff0c\u5f9e\u800c\u505a\u51fa\u66f4\u660e\u667a\u7684\u6c7a\u7b56\u3002<\/p>\n<h2 id=\"%e4%bd%bf%e7%94%a8%e7%b4%a2%e5%bc%95%e5%84%aa%e5%8c%96%e6%9f%a5%e8%a9%a2%e6%80%a7%e8%83%bd-VnizfYaqjY\">\u4f7f\u7528\u7d22\u5f15\u512a\u5316\u67e5\u8a62\u6027\u80fd<\/h2>\n<p>\u5728\u6578\u64da\u5eab\u4e2d\uff0c\u7d22\u5f15\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\u3002\u5c0d\u65bc\u5b57\u7b26\u5b57\u6bb5\uff0c\u9078\u64c7\u5408\u9069\u7684\u7d22\u5f15\u985e\u578b\u548c\u5b57\u7b26\u9577\u5ea6\u53ef\u4ee5\u9032\u4e00\u6b65\u512a\u5316\u6027\u80fd\u3002\u4f8b\u5982\uff0c\u5c0d\u65bcVARCHAR\u5b57\u6bb5\uff0c\u60a8\u53ef\u4ee5\u8003\u616e\u53ea\u5c0d\u524d\u5e7e\u500b\u5b57\u7b26\u9032\u884c\u7d22\u5f15\uff0c\u9019\u6a23\u53ef\u4ee5\u6e1b\u5c11\u7d22\u5f15\u7684\u5927\u5c0f\uff0c\u63d0\u9ad8\u67e5\u8a62\u901f\u5ea6\u3002<\/p>\n<pre><code>CREATE INDEX idx_username ON users (username(10));<\/code><\/pre>\n<p>\u9019\u6a23\u7684\u7d22\u5f15\u5c07\u53ea\u5c0d\u7528\u6236\u540d\u7684\u524d10\u500b\u5b57\u7b26\u9032\u884c\u7d22\u5f15\uff0c\u5f9e\u800c\u7bc0\u7701\u7a7a\u9593\u4e26\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\u3002<\/p>\n<h2 id=\"%e5%ae%9a%e6%9c%9f%e5%af%a9%e6%9f%a5%e5%92%8c%e8%aa%bf%e6%95%b4-VnizfYaqjY\">\u5b9a\u671f\u5be9\u67e5\u548c\u8abf\u6574<\/h2>\n<p>\u6578\u64da\u5eab\u7684\u9700\u6c42\u96a8\u8457\u6642\u9593\u7684\u63a8\u79fb\u53ef\u80fd\u6703\u767c\u751f\u8b8a\u5316\uff0c\u56e0\u6b64\u5b9a\u671f\u5be9\u67e5\u548c\u8abf\u6574\u5b57\u7b26\u9577\u5ea6\u662f\u5fc5\u8981\u7684\u3002\u901a\u904e\u76e3\u63a7\u6578\u64da\u5eab\u6027\u80fd\u548c\u5b58\u5132\u4f7f\u7528\u60c5\u6cc1\uff0c\u60a8\u53ef\u4ee5\u53ca\u6642\u8abf\u6574\u5b57\u7b26\u9577\u5ea6\uff0c\u4ee5\u9069\u61c9\u65b0\u7684\u9700\u6c42\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-VnizfYaqjY\">\u7e3d\u7d50<\/h2>\n<p>\u512a\u5316\u6578\u64da\u5eab\u5b57\u7b26\u9577\u5ea6\u662f\u4e00\u500b\u91cd\u8981\u7684\u904e\u7a0b\uff0c\u6d89\u53ca\u9078\u64c7\u5408\u9069\u7684\u6578\u64da\u985e\u578b\u3001\u5206\u6790\u6578\u64da\u9700\u6c42\u3001\u4f7f\u7528\u7d22\u5f15\u4ee5\u53ca\u5b9a\u671f\u5be9\u67e5\u548c\u8abf\u6574\u3002\u901a\u904e\u9019\u4e9b\u65b9\u6cd5\uff0c\u60a8\u53ef\u4ee5\u63d0\u9ad8\u6578\u64da\u5eab\u7684\u6027\u80fd\u548c\u6548\u7387\uff0c\u5f9e\u800c\u652f\u6301\u66f4\u9ad8\u6548\u7684\u61c9\u7528\u7a0b\u5e8f\u904b\u884c\u3002\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\u5e6b\u52a9\u60a8\u512a\u5316\u6578\u64da\u5eab\u6027\u80fd\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5b78\u7fd2\u5982\u4f55\u512a\u5316\u6578\u64da\u5eab\u4e2d\u7684\u5b57\u7b26\u9577\u5ea6\uff0c\u63d0\u9ad8\u5b58\u5132\u6548\u7387\uff0c\u589e\u5f37\u67e5\u8a62\u6027\u80fd\uff0c\u4e26\u6e1b\u5c11\u8cc7\u6e90\u6d6a\u8cbb\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-179432","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/179432","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=179432"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/179432\/revisions"}],"predecessor-version":[{"id":179433,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/179432\/revisions\/179433"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=179432"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=179432"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=179432"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}