{"id":33953,"date":"2023-06-10T18:55:10","date_gmt":"2023-06-10T10:55:10","guid":{"rendered":"https:\/\/docs.pingcode.com\/?p=33953"},"modified":"2023-07-31T02:07:45","modified_gmt":"2023-07-30T18:07:45","slug":"mysql-varchar-%e4%ba%8c%e8%bf%9b%e5%88%b6%e6%a8%a1%e5%bc%8f%e6%98%af%e4%bb%80%e4%b9%88","status":"publish","type":"post","link":"https:\/\/docs.pingcode.com\/ask\/33953.html","title":{"rendered":"MySQL varchar \u4e8c\u8fdb\u5236\u6a21\u5f0f\u662f\u4ec0\u4e48"},"content":{"rendered":"
\n

MySQL varchar \u4e8c\u8fdb\u5236\u6a21\u5f0f\u662fVARCHAR\u7c7b\u578b\u7684\u4e00\u79cd\u5b50\u7c7b\u578b\uff0c\u901a\u5e38\u7528\u4e8e\u5b58\u50a8\u4e8c\u8fdb\u5236\u6570\u636e\u3002\u5728\u4e8c\u8fdb\u5236\u6a21\u5f0f\u4e0b\uff0cVARCHAR\u7c7b\u578b\u7684\u957f\u5ea6\u9650\u5236\u662f255\u4e2a\u5b57\u7b26\u3002\u901a\u5e38\u60c5\u51b5\u4e0b\uff0cVARCHAR\u7c7b\u578b\u5b58\u50a8\u7684\u662f\u7eaf\u6587\u672c\u5b57\u7b26\u6570\u636e\uff0c\u800c\u4e0d\u662f\u4e8c\u8fdb\u5236\u6570\u636e\u3002<\/p>\n<\/blockquote>\n

\n
\"\"<\/figure>\n<\/div>\n

\u4e00\u3001MySQL varchar \u4e8c\u8fdb\u5236\u6a21\u5f0f\u662f\u4ec0\u4e48<\/h2>\n

MySQL varchar \u4e8c\u8fdb\u5236\u6a21\u5f0f\u662fVARCHAR\u7c7b\u578b\u7684\u4e00\u79cd\u5b50\u7c7b\u578b\uff0c\u901a\u5e38\u7528\u4e8e\u5b58\u50a8\u4e8c\u8fdb\u5236\u6570\u636e\u3002\u5728\u4e8c\u8fdb\u5236\u6a21\u5f0f\u4e0b\uff0cVARCHAR\u7c7b\u578b\u7684\u957f\u5ea6\u9650\u5236\u662f255\u4e2a\u5b57\u7b26\u3002\u901a\u5e38\u60c5\u51b5\u4e0b\uff0cVARCHAR\u7c7b\u578b\u5b58\u50a8\u7684\u662f\u7eaf\u6587\u672c\u5b57\u7b26\u6570\u636e\uff0c\u800c\u4e0d\u662f\u4e8c\u8fdb\u5236\u6570\u636e\u3002\u5f53\u5b58\u50a8\u4e8c\u8fdb\u5236\u6570\u636e\u65f6\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e8c\u8fdb\u5236\u6a21\u5f0f\u7684VARCHAR\u7c7b\u578b\u3002\u5728MySQL\u4e2d\uff0cVARCHAR\u662f\u4e00\u79cd\u53ef\u53d8\u957f\u5ea6\u7684\u5b57\u7b26\u7c7b\u578b\uff0c\u7528\u4e8e\u5b58\u50a8\u7eaf\u6587\u672c\u5b57\u7b26\u6570\u636e\uff0c\u975e\u5e38\u591a\u53ef\u5b58\u50a865535\u4e2a\u5b57\u7b26\u3002VARCHAR\u7c7b\u578b\u53ef\u4ee5\u4f7f\u7528\u591a\u79cd\u4e0d\u540c\u7684\u5b57\u7b26\u96c6\u8fdb\u884c\u5b58\u50a8\uff0c\u5305\u62ecASCII\u548cUNICODE\u7b49\u3002<\/p>\n

\u4e8c\u8fdb\u5236\u6a21\u5f0f\u7684VARCHAR\u7c7b\u578b\u5c06\u6587\u672c\u6570\u636e\u89c6\u4e3a\u4e00\u7ec4\u4e8c\u8fdb\u5236\u6570\u636e\uff0c\u5e76\u4f7f\u7528\u5b57\u8282\u7684\u65b9\u5f0f\u5bf9\u5176\u8fdb\u884c\u5b58\u50a8\u548c\u68c0\u7d22\uff0c\u4e0d\u540c\u4e8e\u975e\u4e8c\u8fdb\u5236\u6a21\u5f0f\u7684VARCHAR\u7c7b\u578b\u3002\u5bf9\u4e8e\u957f\u6587\u672c\u6570\u636e\uff0c\u4f7f\u7528\u4e8c\u8fdb\u5236\u6a21\u5f0f\u7684VARCHAR\u7c7b\u578b\u53ef\u80fd\u4f1a\u5bfc\u81f4\u5b58\u50a8\u7a7a\u95f4\u7684\u6d6a\u8d39\u548c\u67e5\u8be2\u6548\u7387\u7684\u964d\u4f4e\u3002\u56e0\u6b64\uff0c\u5728\u4f7f\u7528VARCHAR\u7c7b\u578b\u5b58\u50a8\u4e8c\u8fdb\u5236\u6570\u636e\u65f6\uff0c\u9700\u8981\u901a\u8fc7\u5408\u7406\u7684\u6570\u636e\u7c7b\u578b\u548c\u5b58\u50a8\u65b9\u5f0f\u6765\u4f18\u5316\u5b58\u50a8\u7a7a\u95f4\u548c\u6027\u80fd\u3002<\/p>\n

\u4e8c\u3001MySQL\u4ecb\u7ecd<\/h2>\n

1\u3001\u7b80\u4ecb<\/h3>\n

MySQL\u662f\u4e00\u4e2a\u5173\u7cfb\u578b\u6570\u636e\u5e93\u7ba1\u7406\u7cfb\u7edf\uff0c\u7531\u745e\u5178MySQL AB\u516c\u53f8\u5f00\u53d1\uff0c\u5c5e\u4e8e Oracle \u65d7\u4e0b\u4ea7\u54c1\u3002MySQL\u662f\u6700\u6d41\u884c\u7684\u5173\u7cfb\u578b\u6570\u636e\u5e93\u7ba1\u7406\u7cfb\u7edf\u4e4b\u4e00\uff0c\u5728 WEB \u5e94\u7528\u65b9\u9762\uff0cMySQL\u662f\u8f83\u597d\u7684 RDBMS\uff08Relational Database Management System\uff0c\u5173\u7cfb\u6570\u636e\u5e93\u7ba1\u7406\u7cfb\u7edf\uff09\u5e94\u7528\u8f6f\u4ef6\u4e4b\u4e00\u3002MySQL\u662f\u4e00\u79cd\u5173\u7cfb\u578b\u6570\u636e\u5e93\u7ba1\u7406\u7cfb\u7edf\uff0c\u5173\u7cfb\u6570\u636e\u5e93\u5c06\u6570\u636e\u4fdd\u5b58\u5728\u4e0d\u540c\u7684\u8868\u4e2d\uff0c\u800c\u4e0d\u662f\u5c06\u6240\u6709\u6570\u636e\u653e\u5728\u4e00\u4e2a\u5927\u4ed3\u5e93\u5185\uff0c\u8fd9\u6837\u5c31\u589e\u52a0\u4e86\u901f\u5ea6\u5e76\u63d0\u9ad8\u4e86\u7075\u6d3b\u6027\u3002MySQL\u6240\u4f7f\u7528\u7684 SQL \u8bed\u8a00\u662f\u7528\u4e8e\u8bbf\u95ee\u6570\u636e\u5e93\u7684\u6700\u5e38\u7528\u6807\u51c6\u5316\u8bed\u8a00\u3002MySQL\u8f6f\u4ef6\u91c7\u7528\u4e86\u53cc\u6388\u6743\u653f\u7b56\uff0c\u5206\u4e3a\u793e\u533a\u7248\u548c\u5546\u4e1a\u7248\uff0c\u7531\u4e8e\u5176\u4f53\u79ef\u5c0f\u3001\u901f\u5ea6\u5feb\u3001\u603b\u4f53\u62e5\u6709\u6210\u672c\u4f4e\uff0c\u5c24\u5176\u662f\u5f00\u653e\u6e90\u7801\u8fd9\u4e00\u7279\u70b9\uff0c\u4e00\u822c\u4e2d\u5c0f\u578b\u548c\u5927\u578b\u7f51\u7ad9\u7684\u5f00\u53d1\u90fd\u9009\u62e9MySQL\u4f5c\u4e3a\u7f51\u7ad9\u6570\u636e\u5e93\u3002<\/p>\n

2\u3001\u7cfb\u7edf\u7279\u6027<\/h3>\n
    \n
  • MySQL\u4f7f\u7528 C\u548c C++\u7f16\u5199\uff0c\u5e76\u4f7f\u7528\u4e86\u591a\u79cd\u7f16\u8bd1\u5668\u8fdb\u884c\u6d4b\u8bd5\uff0c\u4fdd\u8bc1\u4e86\u6e90\u4ee3\u7801\u7684\u53ef\u79fb\u690d\u6027<\/li>\n
  • \u652f\u6301\u00a0AIX\u3001FreeBSD\u3001HP-UX\u3001Linux\u3001Mac OS\u3001NovellNetware\u3001OpenBSD\u3001OS\/2 Wrap\u3001Solaris\u3001Windows\u7b49\u591a\u79cd\u64cd\u4f5c\u7cfb\u7edf<\/li>\n
  • \u4e3a\u591a\u79cd\u7f16\u7a0b\u8bed\u8a00\u63d0\u4f9b\u4e86\u00a0API\u3002\u8fd9\u4e9b\u7f16\u7a0b\u8bed\u8a00\u5305\u62ec C\u3001C++\u3001Python\u3001Java\u3001Perl\u3001PHP\u3001Eiffel\u3001Ruby\u3001.NET\u548c Tcl \u7b49<\/li>\n
  • \u652f\u6301\u591a\u7ebf\u7a0b\uff0c\u5145\u5206\u5229\u7528 CPU \u8d44\u6e90<\/li>\n
  • \u4f18\u5316\u7684\u00a0SQL\u67e5\u8be2\u7b97\u6cd5\uff0c\u6709\u6548\u5730\u63d0\u9ad8\u67e5\u8be2\u901f\u5ea6<\/li>\n
  • \u65e2\u80fd\u591f\u4f5c\u4e3a\u4e00\u4e2a\u5355\u72ec\u7684\u5e94\u7528\u7a0b\u5e8f\u5e94\u7528\u5728\u5ba2\u6237\u7aef\u670d\u52a1\u5668\u7f51\u7edc\u73af\u5883\u4e2d\uff0c\u4e5f\u80fd\u591f\u4f5c\u4e3a\u4e00\u4e2a\u5e93\u800c\u5d4c\u5165\u5230\u5176\u4ed6\u7684\u8f6f\u4ef6\u4e2d<\/li>\n
  • \u63d0\u4f9b\u591a\u8bed\u8a00\u652f\u6301\uff0c\u5e38\u89c1\u7684\u7f16\u7801\u5982\u4e2d\u6587\u7684\u00a0GB 2312\u3001BIG5\uff0c\u65e5\u6587\u7684\u00a0Shift_JIS\u7b49\u90fd\u53ef\u4ee5\u7528\u4f5c\u6570\u636e\u8868\u540d\u548c\u6570\u636e\u5217\u540d<\/li>\n
  • \u63d0\u4f9b\u00a0TCP\/IP\u3001ODBC\u00a0\u548c\u00a0JDBC\u7b49\u591a\u79cd\u6570\u636e\u5e93\u8fde\u63a5\u9014\u5f84<\/li>\n
  • \u63d0\u4f9b\u7528\u4e8e\u7ba1\u7406\u3001\u68c0\u67e5\u3001\u4f18\u5316\u6570\u636e\u5e93\u64cd\u4f5c\u7684\u7ba1\u7406\u5de5\u5177<\/li>\n
  • \u652f\u6301\u5927\u578b\u7684\u6570\u636e\u5e93\u3002\u53ef\u4ee5\u5904\u7406\u62e5\u6709\u4e0a\u5343\u4e07\u6761\u8bb0\u5f55\u7684\u5927\u578b\u6570\u636e\u5e93<\/li>\n
  • \u652f\u6301\u591a\u79cd\u5b58\u50a8\u5f15\u64ce<\/li>\n
  • MySQL \u662f\u5f00\u6e90\u7684\uff0c\u6240\u4ee5\u4f60\u4e0d\u9700\u8981\u652f\u4ed8\u989d\u5916\u7684\u8d39\u7528<\/li>\n
  • MySQL \u4f7f\u7528\u6807\u51c6\u7684\u00a0SQL\u6570\u636e\u8bed\u8a00\u5f62\u5f0f<\/li>\n
  • MySQL \u5bf9 PHP \u6709\u5f88\u597d\u7684\u652f\u6301\uff0cPHP\u662f\u6bd4\u8f83\u6d41\u884c\u7684 Web \u5f00\u53d1\u8bed\u8a00<\/li>\n
  • MySQL\u662f\u53ef\u4ee5\u5b9a\u5236\u7684\uff0c\u91c7\u7528\u4e86 GPL\u534f\u8bae\uff0c\u4f60\u53ef\u4ee5\u4fee\u6539\u6e90\u7801\u6765\u5f00\u53d1\u81ea\u5df1\u7684 MySQL \u7cfb\u7edf<\/li>\n
  • \u5728\u7ebf DDL\/\u66f4\u6539\u529f\u80fd\uff0c\u6570\u636e\u67b6\u6784\u652f\u6301\u52a8\u6001\u5e94\u7528\u7a0b\u5e8f\u548c\u5f00\u53d1\u4eba\u5458\u7075\u6d3b\u6027<\/li>\n
  • \u590d\u5236\u5168\u5c40\u4e8b\u52a1\u6807\u8bc6\uff0c\u53ef\u652f\u6301\u81ea\u6211\u4fee\u590d\u5f0f\u96c6\u7fa4<\/li>\n
  • \u590d\u5236\u65e0\u5d29\u6e83\u4ece\u673a\uff0c\u53ef\u63d0\u9ad8\u53ef\u7528\u6027<\/li>\n
  • \u590d\u5236\u591a\u7ebf\u7a0b\u4ece\u673a\uff0c\u53ef\u63d0\u9ad8\u6027\u80fd<\/li>\n
  • 3\u500d\u66f4\u5feb\u7684\u6027\u80fd<\/li>\n
  • \u65b0\u7684\u4f18\u5316\u5668<\/li>\n
  • \u539f\u751fJSON\u652f\u6301<\/li>\n
  • \u591a\u6e90\u590d\u5236<\/li>\n
  • GIS\u7684\u7a7a\u95f4\u6269\u5c55<\/li>\n<\/ul>\n

    3\u3001\u5b58\u50a8\u5f15\u64ce<\/h3>\n
      \n
    • MyISAM<\/strong>\uff1aMySQL 5.0 \u4e4b\u524d\u7684\u9ed8\u8ba4\u6570\u636e\u5e93\u5f15\u64ce\uff0c\u6700\u4e3a\u5e38\u7528\u3002\u62e5\u6709\u8f83\u9ad8\u7684\u63d2\u5165\uff0c\u67e5\u8be2\u901f\u5ea6\uff0c\u4f46\u4e0d\u652f\u6301\u4e8b\u52a1<\/li>\n
    • InnoDB<\/strong>\uff1a\u4e8b\u52a1\u578b\u6570\u636e\u5e93\u7684\u4f18\u9009\u5f15\u64ce\uff0c\u652f\u6301ACID\u4e8b\u52a1\uff0c\u652f\u6301\u884c\u7ea7\u9501\u5b9a\uff0cMySQL 5.5 \u8d77\u6210\u4e3a\u9ed8\u8ba4\u6570\u636e\u5e93\u5f15\u64ce<\/li>\n
    • BDB<\/strong>\uff1a\u6e90\u81ea\u00a0Berkeley DB\uff0c\u4e8b\u52a1\u578b\u6570\u636e\u5e93\u7684\u53e6\u4e00\u79cd\u9009\u62e9\uff0c\u652f\u6301Commit \u548cRollback \u7b49\u5176\u4ed6\u4e8b\u52a1\u7279\u6027<\/li>\n
    • Memory<\/strong>\uff1a\u6240\u6709\u6570\u636e\u7f6e\u4e8e\u5185\u5b58\u7684\u5b58\u50a8\u5f15\u64ce\uff0c\u62e5\u6709\u6781\u9ad8\u7684\u63d2\u5165\uff0c\u66f4\u65b0\u548c\u67e5\u8be2\u6548\u7387\u3002\u4f46\u662f\u4f1a\u5360\u7528\u548c\u6570\u636e\u91cf\u6210\u6b63\u6bd4\u7684\u5185\u5b58\u7a7a\u95f4\u3002\u5e76\u4e14\u5176\u5185\u5bb9\u4f1a\u5728 MySQL \u91cd\u65b0\u542f\u52a8\u65f6\u4e22\u5931<\/li>\n
    • Merge<\/strong>\uff1a\u5c06\u4e00\u5b9a\u6570\u91cf\u7684 MyISAM \u8868\u8054\u5408\u800c\u6210\u4e00\u4e2a\u6574\u4f53\uff0c\u5728\u8d85\u5927\u89c4\u6a21\u6570\u636e\u5b58\u50a8\u65f6\u5f88\u6709\u7528<\/li>\n
    • Archive<\/strong>\uff1a\u975e\u5e38\u9002\u5408\u5b58\u50a8\u5927\u91cf\u7684\u72ec\u7acb\u7684\uff0c\u4f5c\u4e3a\u5386\u53f2\u8bb0\u5f55\u7684\u6570\u636e\u3002\u56e0\u4e3a\u5b83\u4eec\u4e0d\u7ecf\u5e38\u88ab\u8bfb\u53d6\u3002Archive \u62e5\u6709\u9ad8\u6548\u7684\u63d2\u5165\u901f\u5ea6\uff0c\u4f46\u5176\u5bf9\u67e5\u8be2\u7684\u652f\u6301\u76f8\u5bf9\u8f83\u5dee<\/li>\n
    • Federated<\/strong>\uff1a\u5c06\u4e0d\u540c\u7684 MySQL \u670d\u52a1\u5668\u8054\u5408\u8d77\u6765\uff0c\u903b\u8f91\u4e0a\u7ec4\u6210\u4e00\u4e2a\u5b8c\u6574\u7684\u6570\u636e\u5e93\u3002\u975e\u5e38\u9002\u5408\u5206\u5e03\u5f0f\u5e94\u7528<\/li>\n
    • Cluster\/NDB<\/strong>\uff1a\u9ad8\u5197\u4f59\u7684\u5b58\u50a8\u5f15\u64ce\uff0c\u7528\u591a\u53f0\u6570\u636e\u673a\u5668\u8054\u5408\u63d0\u4f9b\u670d\u52a1\u4ee5\u63d0\u9ad8\u6574\u4f53\u6027\u80fd\u548c\u5b89\u5168\u6027\u3002\u9002\u5408\u6570\u636e\u91cf\u5927\uff0c\u5b89\u5168\u548c\u6027\u80fd\u8981\u6c42\u9ad8\u7684\u5e94\u7528<\/li>\n
    • CSV<\/strong>\uff1a\u903b\u8f91\u4e0a\u7531\u9017\u53f7\u5206\u5272\u6570\u636e\u7684\u5b58\u50a8\u5f15\u64ce\u3002\u5b83\u4f1a\u5728\u6570\u636e\u5e93\u5b50\u76ee\u5f55\u91cc\u4e3a\u6bcf\u4e2a\u6570\u636e\u8868\u521b\u5efa\u4e00\u4e2a .csv \u6587\u4ef6\u3002\u8fd9\u662f\u4e00\u79cd\u666e\u901a\u6587\u672c\u6587\u4ef6\uff0c\u6bcf\u4e2a\u6570\u636e\u884c\u5360\u7528\u4e00\u4e2a\u6587\u672c\u884c\u3002CSV \u5b58\u50a8\u5f15\u64ce\u4e0d\u652f\u6301\u7d22\u5f15<\/li>\n
    • BlackHole<\/strong>\uff1a\u9ed1\u6d1e\u5f15\u64ce\uff0c\u5199\u5165\u7684\u4efb\u4f55\u6570\u636e\u90fd\u4f1a\u6d88\u5931\uff0c\u4e00\u822c\u7528\u4e8e\u8bb0\u5f55 binlog \u505a\u590d\u5236\u7684\u4e2d\u7ee7<\/li>\n
    • EXAMPLE<\/strong>\uff1a\u5b58\u50a8\u5f15\u64ce\u662f\u4e00\u4e2a\u4e0d\u505a\u4efb\u4f55\u4e8b\u60c5\u7684\u5b58\u6839\u5f15\u64ce\u3002\u5b83\u7684\u76ee\u7684\u662f\u4f5c\u4e3a MySQL\u00a0\u6e90\u4ee3\u7801\u4e2d\u7684\u4e00\u4e2a\u4f8b\u5b50\uff0c\u7528\u6765\u6f14\u793a\u5982\u4f55\u5f00\u59cb\u7f16\u5199\u4e00\u4e2a\u65b0\u5b58\u50a8\u5f15\u64ce\u3002\u540c\u6837\uff0c\u5b83\u7684\u4e3b\u8981\u5174\u8da3\u662f\u5bf9\u5f00\u53d1\u8005\u3002EXAMPLE \u5b58\u50a8\u5f15\u64ce\u4e0d\u652f\u6301\u7f16\u7d22\u5f15<\/li>\n<\/ul>\n

      4\u3001\u67e5\u8be2\u4e0e\u7d22\u5f15<\/h3>\n

      \u53ea\u6709\u5f53\u6570\u636e\u5e93\u91cc\u5df2\u7ecf\u6709\u4e86\u8db3\u591f\u591a\u7684\u6d4b\u8bd5\u6570\u636e\u65f6\uff0c\u5b83\u7684\u6027\u80fd\u6d4b\u8bd5\u7ed3\u679c\u624d\u6709\u5b9e\u9645\u53c2\u8003\u4ef7\u503c\u3002\u5982\u679c\u5728\u6d4b\u8bd5\u6570\u636e\u5e93\u91cc\u53ea\u6709\u51e0\u767e\u6761\u6570\u636e\u8bb0\u5f55\uff0c\u5b83\u4eec\u5f80\u5f80\u5728\u6267\u884c\u5b8c\u540d\u5217\u524d\u8305\u6761\u67e5\u8be2\u547d\u4ee4\u4e4b\u540e\u5c31\u88ab\u5168\u90e8\u52a0\u8f7d\u5230\u5185\u5b58\u91cc\uff0c\u8fd9\u5c06\u4f7f\u540e\u7eed\u7684\u67e5\u8be2\u547d\u4ee4\u90fd\u6267\u884c\u5f97\u975e\u5e38\u5feb\u2013\u4e0d\u7ba1\u6709\u6ca1\u6709\u4f7f\u7528\u7d22\u5f15\u3002\u53ea\u6709\u5f53\u6570\u636e\u5e93\u91cc\u7684\u8bb0\u5f55\u8d85\u8fc7\u4e86 1000 \u6761\u3001\u6570\u636e\u603b\u91cf\u4e5f\u8d85\u8fc7\u4e86 MySQL \u670d\u52a1\u5668\u4e0a\u7684\u5185\u5b58\u603b\u91cf\u65f6\uff0c\u6570\u636e\u5e93\u7684\u6027\u80fd\u6d4b\u8bd5\u7ed3\u679c\u624d\u6709\u610f\u4e49\u3002<\/p>\n

      \u5728\u4e0d\u786e\u5b9a\u5e94\u8be5\u5728\u54ea\u4e9b\u6570\u636e\u5217\u4e0a\u521b\u5efa\u7d22\u5f15\u7684\u65f6\u5019\uff0c\u4eba\u4eec\u4ece EXPLAIN SELECT \u547d\u4ee4\u90a3\u91cc\u5f80\u5f80\u53ef\u4ee5\u83b7\u5f97\u4e00\u4e9b\u5e2e\u52a9\u3002\u8fd9\u5176\u5b9e\u53ea\u662f\u7b80\u5355\u5730\u7ed9\u4e00\u6761\u666e\u901a\u7684 SELECT \u547d\u4ee4\u52a0\u4e00\u4e2a EXPLAIN \u5173\u952e\u5b57\u4f5c\u4e3a\u524d\u7f00\u800c\u5df2\u3002\u6709\u4e86\u8fd9\u4e2a\u5173\u952e\u5b57\uff0cMySQL \u5c06\u4e0d\u662f\u53bb\u6267\u884c\u90a3\u6761 SELECT \u547d\u4ee4\uff0c\u800c\u662f\u53bb\u5bf9\u5b83\u8fdb\u884c\u5206\u6790\u3002MySQL \u5c06\u4ee5\u8868\u683c\u7684\u5f62\u5f0f\u628a\u67e5\u8be2\u7684\u6267\u884c\u8fc7\u7a0b\u548c\u7528\u5230\u7684\u7d22\u5f15\u7b49\u4fe1\u606f\u5217\u51fa\u6765\u3002<\/p>\n

      \u5728 EXPLAIN \u547d\u4ee4\u7684\u8f93\u51fa\u7ed3\u679c\u91cc\uff0c\u7b2c1\u5217\u662f\u4ece\u6570\u636e\u5e93\u8bfb\u53d6\u7684\u6570\u636e\u8868\u7684\u540d\u5b57\uff0c\u5b83\u4eec\u6309\u88ab\u8bfb\u53d6\u7684\u5148\u540e\u987a\u5e8f\u6392\u5217\u3002type\u5217\u6307\u5b9a\u4e86\u672c\u6570\u636e\u8868\u4e0e\u5176\u5b83\u6570\u636e\u8868\u4e4b\u95f4\u7684\u5173\u8054\u5173\u7cfb\uff08JOIN\uff09\u3002\u5728\u5404\u79cd\u7c7b\u578b\u7684\u5173\u8054\u5173\u7cfb\u5f53\u4e2d\uff0c\u6548\u7387\u8f83\u9ad8\u7684\u662f system\uff0c\u7136\u540e\u4f9d\u6b21\u662f const\u3001eq_ref\u3001ref\u3001range\u3001index \u548c All\uff08All \u7684\u610f\u601d\u662f\uff1a\u5bf9\u5e94\u4e8e\u4e0a\u4e00\u7ea7\u6570\u636e\u8868\u91cc\u7684\u6bcf\u4e00\u6761\u8bb0\u5f55\uff0c\u8fd9\u4e2a\u6570\u636e\u8868\u91cc\u7684\u6240\u6709\u8bb0\u5f55\u90fd\u5fc5\u987b\u88ab\u8bfb\u53d6\u4e00\u904d\uff0c\u8fd9\u79cd\u60c5\u51b5\u5f80\u5f80\u53ef\u4ee5\u7528\u4e00\u7d22\u5f15\u6765\u907f\u514d\uff09\u3002<\/p>\n

      possible_keys \u6570\u636e\u5217\u7ed9\u51fa\u4e86 MySQL \u5728\u641c\u7d22\u6570\u636e\u8bb0\u5f55\u65f6\u53ef\u9009\u7528\u7684\u5404\u4e2a\u7d22\u5f15\u3002key \u6570\u636e\u5217\u662f MySQL \u5b9e\u9645\u9009\u7528\u7684\u7d22\u5f15\uff0c\u8fd9\u4e2a\u7d22\u5f15\u6309\u5b57\u8282\u8ba1\u7b97\u7684\u957f\u5ea6\u5728 key_len \u6570\u636e\u5217\u91cc\u7ed9\u51fa\u3002\u6bd4\u5982\u8bf4\uff0c\u5bf9\u4e8e\u4e00\u4e2a INTEGER \u6570\u636e\u5217\u7684\u7d22\u5f15\uff0c\u8fd9\u4e2a\u5b57\u8282\u957f\u5ea6\u5c06\u662f4\u3002\u5982\u679c\u7528\u5230\u4e86\u590d\u5408\u7d22\u5f15\uff0c\u5728 key_len \u6570\u636e\u5217\u91cc\u8fd8\u53ef\u4ee5\u770b\u5230 MySQL \u5177\u4f53\u4f7f\u7528\u4e86\u5b83\u7684\u54ea\u4e9b\u90e8\u5206\u3002\u4f5c\u4e3a\u4e00\u822c\u89c4\u5f8b\uff0ckey_len \u6570\u636e\u5217\u91cc\u7684\u503c\u8d8a\u5c0f\u8d8a\u597d\u3002<\/p>\n

      ref \u6570\u636e\u5217\u7ed9\u51fa\u4e86\u5173\u8054\u5173\u7cfb\u4e2d\u53e6\u4e00\u4e2a\u6570\u636e\u8868\u91cc\u7684\u6570\u636e\u5217\u7684\u540d\u5b57\u3002row \u6570\u636e\u5217\u662f MySQL \u5728\u6267\u884c\u8fd9\u4e2a\u67e5\u8be2\u65f6\u9884\u8ba1\u4f1a\u4ece\u8fd9\u4e2a\u6570\u636e\u8868\u91cc\u8bfb\u51fa\u7684\u6570\u636e\u884c\u7684\u4e2a\u6570\u3002row \u6570\u636e\u5217\u91cc\u7684\u6240\u6709\u6570\u5b57\u7684\u4e58\u79ef\u53ef\u4ee5\u5927\u81f4\u4e86\u89e3\u8fd9\u4e2a\u67e5\u8be2\u9700\u8981\u5904\u7406\u591a\u5c11\u7ec4\u5408\u3002<\/p>\n

      \u6700\u540e\uff0cextra \u6570\u636e\u5217\u63d0\u4f9b\u4e86\u4e0e JOIN \u64cd\u4f5c\u6709\u5173\u7684\u66f4\u591a\u4fe1\u606f\uff0c\u6bd4\u5982\u8bf4\uff0c\u5982\u679c MySQL \u5728\u6267\u884c\u8fd9\u4e2a\u67e5\u8be2\u65f6\u5fc5\u987b\u521b\u5efa\u4e00\u4e2a\u4e34\u65f6\u6570\u636e\u8868\uff0c\u5c31\u4f1a\u5728 extra \u5217\u770b\u5230 usingtemporary \u5b57\u6837\u3002<\/p>\n

      \u5ef6\u4f38\u9605\u8bfb1\uff1aMySQL\u7684\u7ba1\u7406\u5de5\u5177<\/em><\/strong><\/p>\n

      \u53ef\u4ee5\u4f7f\u7528\u547d\u4ee4\u884c\u5de5\u5177\u7ba1\u7406 MySQL \u6570\u636e\u5e93\uff08\u547d\u4ee4 mysql \u548c mysqladmin\uff09\uff0c\u4e5f\u53ef\u4ee5\u4ece MySQL \u7684\u7f51\u7ad9\u4e0b\u8f7d\u56fe\u5f62\u7ba1\u7406\u5de5\u5177 MySQL Administrator\uff0cMySQL Query Browser \u548c MySQL Workbench\u3002phpMyAdmin\u662f\u7531 php \u5199\u6210\u7684 MySQL\u8d44\u6599\u5e93\u7cfb\u7edf\u7ba1\u7406\u7a0b\u7a0b\u5e8f\uff0c\u8ba9\u7ba1\u7406\u8005\u53ef\u7528 Web \u754c\u9762\u7ba1\u7406 MySQL \u8d44\u6599\u5e93\u3002phpMyBackupPro\u4e5f\u662f\u7531 PHP \u5199\u6210\u7684\uff0c\u53ef\u4ee5\u900f\u8fc7 Web \u754c\u9762\u521b\u5efa\u548c\u7ba1\u7406\u6570\u636e\u5e93\u3002\u5b83\u53ef\u4ee5\u521b\u5efa\u4f2a cronjobs\uff0c\u53ef\u4ee5\u7528\u6765\u81ea\u52a8\u5728\u67d0\u4e2a\u65f6\u95f4\u6216\u5468\u671f\u5907\u4efd MySQL \u6570\u636e\u5e93\u3002\u53e6\u5916\uff0c\u8fd8\u6709\u5176\u4ed6\u7684 GUI \u7ba1\u7406\u5de5\u5177\uff0c\u4f8b\u5982 mysql-front \u4ee5\u53ca ems mysql manager, navicat\u7b49\u7b49\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"MySQL varchar \u4e8c\u8fdb\u5236\u6a21\u5f0f\u662fVARCHAR\u7c7b\u578b\u7684\u4e00\u79cd\u5b50\u7c7b\u578b\uff0c\u901a\u5e38\u7528\u4e8e\u5b58\u50a8\u4e8c\u8fdb\u5236\u6570\u636e\u3002\u5728\u4e8c\u8fdb\u5236\u6a21\u5f0f\u4e0b […]","protected":false},"author":1,"featured_media":33956,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[37],"tags":[119],"acf":[],"_links":{"self":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/33953"}],"collection":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/comments?post=33953"}],"version-history":[{"count":0,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/33953\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/media\/33956"}],"wp:attachment":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/media?parent=33953"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/categories?post=33953"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/tags?post=33953"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}