{"id":200792,"date":"2025-05-06T08:02:35","date_gmt":"2025-05-06T00:02:35","guid":{"rendered":"https:\/\/server.hk\/cnblog\/200792\/"},"modified":"2025-05-06T08:02:35","modified_gmt":"2025-05-06T00:02:35","slug":"mysql-%e4%b8%ad-key_len-%e4%b8%ba%e4%bd%95%e4%b8%8e%e9%a2%84%e6%9c%9f%e4%b8%8d%e7%ac%a6%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/200792\/","title":{"rendered":"MySQL \u4e2d key_len \u4e3a\u4f55\u4e0e\u9884\u671f\u4e0d\u7b26\uff1f"},"content":{"rendered":"

<\/b> <\/p>\n

MySQL \u4e2d key_len \u4e3a\u4f55\u4e0e\u9884\u671f\u4e0d\u7b26\uff1f<\/h1>\n

\u6570\u636e\u5e93\u5c0f\u767d\u4e00\u679a\uff0c\u6b63\u5728\u4e0d\u65ad\u5b66\u4e60\u79ef\u7d2f\u77e5\u8bc6\uff0c\u73b0\u5c06\u5b66\u4e60\u5230\u7684\u77e5\u8bc6\u8bb0\u5f55\u4e00\u4e0b\uff0c\u4e5f\u662f\u5c06\u6211\u7684\u6240\u5f97\u5206\u4eab\u7ed9\u5927\u5bb6\uff01\u800c\u4eca\u5929\u8fd9\u7bc7\u6587\u7ae0\u300aMySQL \u4e2d key_len \u4e3a\u4f55\u4e0e\u9884\u671f\u4e0d\u7b26\uff1f\u300b\u5e26\u5927\u5bb6\u6765\u4e86\u89e3\u4e00\u4e0b##content_title##\uff0c\u5e0c\u671b\u5bf9\u5927\u5bb6\u7684\u77e5\u8bc6\u79ef\u7d2f\u6709\u6240\u5e2e\u52a9\uff0c\u4ece\u800c\u5f25\u8865\u81ea\u5df1\u7684\u4e0d\u8db3\uff0c\u52a9\u529b\u5b9e\u6218\u5f00\u53d1\uff01<\/p>\n

<\/p>\n

<\/p>\n

MySQL \u4e2d key_len \u7684\u8ba1\u7b97\u65b9\u5f0f<\/strong><\/p>\n

\u4f60\u5728\u8fd0\u884c EXPLAIN \u67e5\u770b\u6267\u884c\u8ba1\u5212\u65f6\uff0c\u6ce8\u610f\u5230\u4e86 key_len \u4e0d\u662f\u4f60\u9884\u671f\u7684 60\uff0c\u800c\u662f 80\u3002\u8fd9\u662f\u56e0\u4e3a MySQL \u4e2d key_len \u7684\u8ba1\u7b97\u65b9\u5f0f\u4e0e\u4f60\u60f3\u8c61\u7684\u4e0d\u540c\u3002<\/p>\n

\u5728 MySQL \u4e2d\uff0cchar \u548c varchar \u7c7b\u578b\u7684\u6570\u636e\u5728\u5b58\u50a8\u65f6\u90fd\u4f1a\u88ab\u8f6c\u6362\u4e3a UTF-8\u3002\u6bcf\u4e2a UTF-8 \u5b57\u7b26\u7684\u957f\u5ea6\u4ece 1 \u5230 4 \u4e2a\u5b57\u8282\u4e0d\u7b49\uff0c\u5177\u4f53\u53d6\u51b3\u4e8e\u5b57\u7b26\u7684\u7f16\u7801\u3002<\/p>\n

\u5bf9\u4e8e char(20) \u7c7b\u578b\u7684\u5217\uff0c\u5b83\u5b9e\u9645\u4e0a\u53ef\u4ee5\u5728\u5b58\u50a8\u4e2d\u5360\u7528\u9ad8\u8fbe 80 \u4e2a\u5b57\u8282\uff0c\u56e0\u4e3a\u6bcf\u4e2a\u5b57\u7b26\u6700\u591a\u53ef\u4ee5\u5360\u7528 4 \u4e2a\u5b57\u8282\u3002\u56e0\u6b64\uff0c\u5373\u4f7f\u8868\u4e2d\u53ea\u6709 3 \u6761\u8bb0\u5f55\uff0ckey_len \u4ecd\u7136\u662f 80\uff0c\u800c\u4e0d\u662f 60\u3002<\/p>\n

\u503c\u5f97\u6ce8\u610f\u7684\u662f\uff0ckey_len \u5e76\u4e0d\u662f\u6307\u8868\u4e2d\u5b9e\u9645\u5b58\u50a8\u7684\u6570\u636e\u5927\u5c0f\uff0c\u800c\u662f\u6307\u7d22\u5f15\u4e2d\u5b58\u50a8\u7684\u6570\u636e\u5927\u5c0f\u3002\u7d22\u5f15\u662f\u6839\u636e\u8868\u4e2d\u7684\u5217\u521b\u5efa\u7684\uff0c\u5b83\u672c\u8d28\u4e0a\u662f\u4e00\u79cd\u5feb\u901f\u67e5\u627e\u8868\u4e2d\u6570\u636e\u7684\u76ee\u5f55\u3002\u7531\u4e8e\u7d22\u5f15\u662f\u6309\u7167\u5347\u5e8f\u6216\u964d\u5e8f\u6392\u5217\u7684\uff0c\u56e0\u6b64\u7d22\u5f15\u4e2d\u7684\u503c\u5fc5\u987b\u6309\u8be5\u987a\u5e8f\u5b58\u50a8\u3002<\/p>\n

\u56e0\u6b64\uff0cMySQL \u4f1a\u4f7f\u7528\u4e00\u79cd\u53eb\u505a\u524d\u7f00\u538b\u7f29\u7684\u6280\u672f\u6765\u5b58\u50a8\u7d22\u5f15\u503c\u3002\u8fd9\u79cd\u6280\u672f\u53ef\u4ee5\u51cf\u5c11\u7d22\u5f15\u4e2d\u5b58\u50a8\u7684\u6570\u636e\u5927\u5c0f\uff0c\u4ece\u800c\u63d0\u9ad8\u67e5\u8be2\u6027\u80fd\u3002\u524d\u7f00\u538b\u7f29\u4f1a\u5220\u9664\u7d22\u5f15\u503c\u4e2d\u91cd\u590d\u7684\u5b57\u7b26\u5e8f\u5217\uff0c\u5e76\u7528\u6307\u5411\u8fd9\u4e9b\u91cd\u590d\u5b57\u7b26\u5e8f\u5217\u7684\u6307\u9488\u4ee3\u66ff\u3002<\/p>\n

\u5728\u4f60\u7684\u4f8b\u5b50\u4e2d\uff0cstudent_name \u7d22\u5f15\u7684\u503c\u90fd\u662f\u4ee5 ‘L’ \u5f00\u5934\u7684\u3002\u56e0\u6b64\uff0cMySQL \u4f1a\u5c06 ‘L’ \u5b57\u7b26\u5b58\u50a8\u4e00\u6b21\uff0c\u5e76\u5728\u5176\u4ed6\u503c\u4e2d\u7528\u6307\u5411 ‘L’ \u5b57\u7b26\u7684\u6307\u9488\u4ee3\u66ff\u3002\u8fd9\u53ef\u4ee5\u5927\u5927\u51cf\u5c11\u7d22\u5f15\u503c\u7684\u5927\u5c0f\uff0c\u4ece\u800c\u964d\u4f4e key_len\u3002<\/p>\n

\u4eca\u5929\u5173\u4e8e\u300aMySQL \u4e2d key_len \u4e3a\u4f55\u4e0e\u9884\u671f\u4e0d\u7b26\uff1f\u300b\u7684\u5185\u5bb9\u4ecb\u7ecd\u5c31\u5230\u6b64\u7ed3\u675f\uff0c\u5982\u679c\u6709\u4ec0\u4e48\u7591\u95ee\u6216\u8005\u5efa\u8bae\uff0c\u53ef\u4ee5\u5728\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\u4e0b\u591a\u591a\u56de\u590d\u4ea4\u6d41\uff1b\u6587\u4e2d\u82e5\u6709\u4e0d\u6b63\u4e4b\u5904\uff0c\u4e5f\u5e0c\u671b\u56de\u590d\u7559\u8a00\u4ee5\u544a\u77e5\uff01<\/p>\n

\n
\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"

MySQL \u4e2d key_len ...<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-200792","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200792","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"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=200792"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200792\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=200792"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=200792"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=200792"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}