{"id":4850,"date":"2024-08-01T22:49:03","date_gmt":"2024-08-01T14:49:03","guid":{"rendered":"https:\/\/xinchewhd.com.cn\/?p=4850"},"modified":"2024-08-02T14:59:02","modified_gmt":"2024-08-02T06:59:02","slug":"%e9%9d%a2%e8%af%95%e5%ae%98%e5%90%ac%e5%88%b0%e6%88%91%e5%af%b9-explain-%e4%bd%bf%e7%94%a8%e7%9a%84%e5%9b%9e%e7%ad%94%e7%ab%96%e8%b5%b7%e4%ba%86%e5%a4%a7%e6%8b%87%e6%8c%87","status":"publish","type":"post","link":"https:\/\/xinchewhd.com.cn\/index.php\/mysql\/%e9%9d%a2%e8%af%95%e5%ae%98%e5%90%ac%e5%88%b0%e6%88%91%e5%af%b9-explain-%e4%bd%bf%e7%94%a8%e7%9a%84%e5%9b%9e%e7%ad%94%e7%ab%96%e8%b5%b7%e4%ba%86%e5%a4%a7%e6%8b%87%e6%8c%87\/","title":{"rendered":"\u9762\u8bd5\u5b98\u542c\u5230\u6211\u5bf9 explain \u4f7f\u7528\u7684\u56de\u7b54\u7ad6\u8d77\u4e86\u5927\u62c7\u6307"},"content":{"rendered":"
\n
\n

\u5f15\u8a00\uff1a\u5728 Java \u6570\u636e\u5e93\u64cd\u4f5c\u4e2d\uff0c\u7406\u89e3 SQL \u8bed\u53e5\u7684\u6267\u884c\u8ba1\u5212\u662f\u4f18\u5316\u67e5\u8be2\u6027\u80fd\u7684\u5173\u952e\u4e4b\u4e00\u3002Explain \u662f\u4e00\u4e2a\u91cd\u8981\u7684 SQL \u8bed\u53e5\uff0c\u5b83\u80fd\u591f\u663e\u793a\u6570\u636e\u5e93\u5982\u4f55\u6267\u884c\u67d0\u4e2a\u67e5\u8be2\uff0c\u5e2e\u52a9\u5f00\u53d1\u8005\u8bc6\u522b\u6027\u80fd\u74f6\u9888\u548c\u4f18\u5316\u67e5\u8be2\u3002\u5728\u9762\u8bd5\u4e2d\uff0c\u88ab\u95ee\u5230\u5982\u4f55\u4f7f\u7528 Explain \u4ee5\u53ca\u5982\u4f55\u5206\u6790\u5176\u8f93\u51fa\u7ed3\u679c\uff0c\u662f\u5bf9\u5f00\u53d1\u8005\u7406\u89e3\u6570\u636e\u5e93\u4f18\u5316\u7684\u4e00\u4e2a\u91cd\u8981\u8003\u6838\u70b9\u3002\u672c\u6587\u5c06\u5e26\u4f60\u6df1\u5165\u4e86\u89e3 Explain \u8bed\u53e5\u7684\u4f7f\u7528\u65b9\u6cd5\u548c\u5206\u6790\u6280\u5de7\uff0c\u5e2e\u52a9\u4f60\u5728\u9762\u8bd5\u548c\u5b9e\u9645\u5f00\u53d1\u4e2d\uff0c\u80fd\u591f\u81ea\u4fe1\u4e14\u6e05\u6670\u5730\u9610\u8ff0\u67e5\u8be2\u4f18\u5316\u7684\u5de5\u4f5c\u539f\u7406\u548c\u5e94\u7528\u573a\u666f\u3002<\/p>\n

\u9898\u76ee<\/span><\/h2>\n

\u9762\u8bd5\u5b98\u542c\u5230\u6211\u5bf9 explain \u4f7f\u7528\u7684\u56de\u7b54\u7ad6\u8d77\u4e86\u5927\u62c7\u6307<\/p>\n

\u63a8\u8350\u89e3\u6790<\/span><\/h2>\n

\u4eca\u5929\u78b0\u89c1\u4e00\u4e2a\u9762\u8bd5\u5b98\u95ee\u6211\uff1a\u7528\u8fc7 explain \u5417\uff1f\u8bf4\u8bf4\u600e\u4e48\u5206\u6790\u7684\uff1f<\/p>\n

\u6211\uff1a\u54c8\u54c8\u54c8\u649e\u6211\u67aa\u53e3\u4e0a\u4e86\uff0c\u8ba9\u6211\u6765\u9707\u60ca\u4f60\u4e00\u4e0b\uff01<\/p>\n

\u6211\uff1a\u4f60\u597d\u9762\u8bd5\u5b98\uff0c\u6211\u5f53\u7136\u7528\u8fc7 explain\uff0c\u6211\u5e73\u65f6\u90fd\u4f1a\u90a3\u5b83\u53bb\u67e5\u770b SQL \u8bed\u53e5\u662f\u5426\u8fd8\u80fd\u4f18\u5316\u3002\u63a5\u4e0b\u6765\u6211\u4ece\u4e3b\u8981\u5c5e\u6027\u8ddf\u5b9e\u9645\u4f8b\u5b50\u6765\u8bb2\u89e3\uff1a<\/p>\n

\u4e3b\u8981\u7684\u5c5e\u6027<\/span><\/h3>\n

id<\/span><\/h4>\n

\u67e5\u8be2\u4e2d\u6bcf\u4e2a SELECT \u5b50\u53e5\u7684\u6807\u8bc6\u7b26\u3002\u7b80\u5355\u67e5\u8be2\u7684 id \u901a\u5e38\u4e3a 1\uff0c\u590d\u6742\u67e5\u8be2\uff08\u5982\u5305\u542b\u5b50\u67e5\u8be2\u6216 UNION\uff09\u7684 id \u4f1a\u6709\u591a\u4e2a\u3002<\/p>\n

select_type<\/span><\/h4>\n

\u63cf\u8ff0\u67e5\u8be2\u7684\u7c7b\u578b\u3002\u6bd4\u5982\uff1a\u7b80\u5355\u67e5\u8be2\u663e\u793a\u4e3a SIMPLE<\/code>\uff0c\u5b50\u67e5\u8be2\u663e\u793a\u4e3a SUBQUERY<\/code>\uff0cUNION \u4e2d\u7684\u7b2c\u4e8c\u4e2a\u548c\u540e\u7eed\u67e5\u8be2\u663e\u793a\u4e3a UNION<\/code>\u3002<\/p>\n

table<\/span><\/h4>\n

\u8868\u540d\u79f0\u8fd9\u4e2a\u5c31\u4e0d\u7528\u518d\u8be6\u7ec6\u89e3\u91ca\u4e86\u5427\u54c8\u54c8\u3002<\/p>\n

partitions<\/span><\/h4>\n

\u8868\u793a\u67e5\u8be2\u6d89\u53ca\u5230\u7684\u5206\u533a\u3002\u5982\u679c\u4f60\u6709\u4f7f\u7528\u5206\u533a\u8868\u7684\u8bdd\u624d\u9700\u8981\u5173\u6ce8\u6b64\u5b57\u6bb5\u3002<\/p>\n

type<\/span><\/h4>\n

\u8868\u793a\u8bbf\u95ee\u7684\u7c7b\u578b\uff0c\u8fd9\u91cc\u4e5f\u53ef\u4ee5\u770b\u51fa\u4f60\u7684 SQL \u7684\u6027\u80fd\u3002\u53ef\u80fd\u7684\u503c\u4ece\u6700\u597d\u5230\u6700\u5dee\u5305\u62ec\uff1asystem<\/code>\u3001const<\/code>\u3001eq_ref<\/code>\u3001ref<\/code>\u3001range<\/code>\u3001index<\/code>\u3001ALL<\/code>\u3002\u5176\u4e2d ALL<\/code> \u8868\u793a\u5168\u8868\u626b\u63cf\uff0c\u6548\u7387\u6700\u4f4e\u3002<\/p>\n

    \n
  • \n
    \n

    system\uff1a<\/p>\n

    \u8868\u793a\u67e5\u8be2\u7684\u8868\u53ea\u6709\u4e00\u884c\uff08\u7cfb\u7edf\u8868\uff09\u3002\u8fd9\u662f\u4e00\u4e2a\u7279\u6b8a\u7684\u60c5\u51b5\uff0c\u4e0d\u5e38\u89c1\u3002<\/p>\n<\/section>\n<\/li>\n

  • \n
    \n

    const\uff1a<\/p>\n

    \u8868\u793a\u67e5\u8be2\u7684\u8868\u6700\u591a\u53ea\u6709\u4e00\u884c\u5339\u914d\u7ed3\u679c\u3002\u8fd9\u901a\u5e38\u53d1\u751f\u5728\u67e5\u8be2\u6761\u4ef6\u662f\u4e3b\u952e<\/strong>\u6216\u552f\u4e00\u7d22\u5f15<\/strong>\uff0c\u5e76\u4e14\u662f\u5e38\u91cf\u6bd4\u8f83\uff0c\u4ee5\u4e0b\u662f\u4e00\u4e2a\u4f7f\u7528\u4e3b\u952e\u67e5\u627e\u7684\u4f8b\u5b50\uff1a<\/p>\n

    CREATE <\/span>INDEX <\/span>idx_department_salary ON <\/span>employees(department_id,salary);<\/code><\/pre>\n
    \u590d\u5408\u7d22\u5f15\u53ef\u4ee5\u4f7f\u67e5\u8be2\u5728\u626b\u63cf department_id<\/code> \u5217\u65f6\uff0c\u540c\u65f6\u6309 salary<\/code> \u5217\u6392\u5e8f\uff0c\u907f\u514d\u989d\u5916\u7684\u6587\u4ef6\u6392\u5e8f\u3002<\/p>\n
    \u518d\u6b21\u6267\u884c\u8ba1\u5212\u5206\u6790<\/strong><\/p>\n
    \u4f18\u5316\u540e\u7684 EXPLAIN<\/code> \u8f93\u51fa\u5982\u4e0b\uff1a<\/p>\n
    \n\n\n\n\n\n
    id<\/th>\nselect_type<\/th>\ntable<\/th>\npartitions<\/th>\ntype<\/th>\npossible_keys<\/th>\nkey<\/th>\nkey_len<\/th>\nref<\/th>\nrows<\/th>\nfiltered<\/th>\nExtra<\/th>\n<\/tr>\n<\/thead>\n
    1<\/td>\nSIMPLE<\/td>\nemployees<\/td>\nNULL<\/td>\nrange<\/td>\nidx_department_salary<\/td>\nidx_department_salary<\/td>\n5<\/td>\nNULL<\/td>\n500<\/td>\n100.00<\/td>\nUsing where<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/section>\n
    6.\u5206\u6790\u4f18\u5316\u540e\u7684\u7ed3\u679c<\/span><\/h4>\n
    \u4ece\u65b0\u7684 EXPLAIN<\/code> \u8f93\u51fa\u4e2d\u53ef\u4ee5\u770b\u51fa\uff1a<\/p>\n
      \n
    • \n
      type<\/strong>: range<\/code>\uff0c\u8868\u793a\u4f7f\u7528\u8303\u56f4\u626b\u63cf\uff0c\u8fd9\u662f\u4e2a\u76f8\u5bf9\u9ad8\u6548\u7684\u8bbf\u95ee\u7c7b\u578b\u3002<\/section>\n<\/li>\n
    • \n
      key<\/strong>: idx_department_salary<\/code>\uff0c\u8868\u793a\u5b9e\u9645\u4f7f\u7528\u4e86\u590d\u5408\u7d22\u5f15\u3002<\/section>\n<\/li>\n
    • \n
      rows<\/strong>: 500\uff0c\u4f30\u8ba1\u8bfb\u53d6\u7684\u884c\u6570\u51cf\u5c11\u4e86\uff0c\u56e0\u4e3a\u7d22\u5f15\u66f4\u7cbe\u786e\u5730\u8986\u76d6\u4e86\u67e5\u8be2\u6761\u4ef6\u3002<\/section>\n<\/li>\n
    • \n
      Extra<\/strong>: \u4ec5\u663e\u793a Using where<\/code>\uff0c\u4e0d\u518d\u9700\u8981\u6587\u4ef6\u6392\u5e8f\uff0c\u56e0\u4e3a\u7d22\u5f15\u5df2\u7ecf\u8986\u76d6\u4e86\u6392\u5e8f\u9700\u6c42\u3002<\/section>\n<\/li>\n<\/ul>\n
      \u662f\u4e0d\u662f\u5206\u6790\u8d77\u6765\u5f88\u7b80\u5355\u54a7\uff0c\u5b8c\u7ed3\u6492\u82b1\uff01\uff01\uff01\uff01\uff0c\u9664\u4e86\u65b0\u589e\u8054\u5408\u7d22\u5f15\u7684\u65b9\u5f0f\uff0c\u4f60\u4eec\u8fd8\u77e5\u9053\u4ec0\u4e48\u4f18\u5316\u7b56\u7565\u5417\uff1f<\/p>\n
      \u63a8\u8350\u6587\u7ae0\u548c\u4e66\u7c4d<\/span><\/h3>\n
      \u6587\u7ae0\uff1ahttps:\/\/zhuanlan.zhihu.com\/p\/86293659<\/p>\n
      \u4e66\u7c4d\uff1a\u300a Java \u6838\u5fc3\u6280\u672f\u5377 I \u300b<\/p>\n
      \u6b22\u8fce\u4ea4\u6d41<\/span><\/h2>\n
      \u5f53\u8c08\u5230Explain \u65f6\uff0c\u6211\u4eec\u53ef\u4ee5\u63a2\u8ba8\u4ee5\u4e0b\u51e0\u4e2a\u95ee\u9898\uff1a<\/p>\n
      1\uff09\u5982\u4f55\u5224\u65ad\u67e5\u8be2\u662f\u5426\u4f7f\u7528\u4e86\u7d22\u5f15\uff1f<\/p>\n
      2\uff09Explain \u8f93\u51fa\u4e2d\u7684 type \u5217\u4ee3\u8868\u4ec0\u4e48\uff1f\u54ea\u4e9b\u7c7b\u578b\u8868\u793a\u67e5\u8be2\u6027\u80fd\u8f83\u597d\uff1f<\/p>\n
      3\uff09\u5982\u4f55\u901a\u8fc7 Explain \u8f93\u51fa\u4e2d\u7684 Explain \u5217\u4f18\u5316\u67e5\u8be2\uff1f<\/p>\n
      \u8fd9\u4e9b\u95ee\u9898\u5c06\u5e2e\u52a9\u6211\u4eec\u6df1\u5165\u4e86\u89e3 Explain \u6267\u884c\u8ba1\u5212\u7684\u6982\u5ff5\u3001\u5e94\u7528\u548c\u539f\u7406\uff0c\u4ece\u800c\u66f4\u597d\u7528\u6765\u89e3\u51b3\u5b9e\u9645\u95ee\u9898\u3002<\/p>\n
      \n
      \u70b9\u71c3\u6c42\u804c\u70ed\u60c5\uff01\u6bcf\u5468\u6301\u7eed\u66f4\u65b0\uff0c\u6d77\u91cf\u9762\u8bd5\u9898\u548c\u5927\u5382\u9762\u7ecf\u7b49\u4f60\u6311\u6218\uff01\u8d76\u7d27\u5173\u6ce8\u9762\u8bd5\u9e2d\u516c\u4f17\u53f7\uff0c\u8f7b\u677e\u5907\u6218\u6625\u62db\u548c\u6691\u671f\u5b9e\u4e60\uff01<\/span><\/p>\n
      \n
      <\/section>\n
      \n<\/section>\n
      \n
      \n
      \n
      \n
      \u5f80\u671f\u63a8\u8350<\/p>\n<\/section>\n<\/section>\n
      \n
      \n
      \n
      \u9762\u8bd5\u5b98\uff1a\u4ec0\u4e48\u662f\u7269\u7406\u5730\u5740\uff0c\u4ec0\u4e48\u662f\u903b\u8f91\u5730\u5740\uff1f<\/p>\n<\/section>\n<\/section>\n
      \n
      \n
      \u8fdb\u7a0b\u4e4b\u95f4\u7684\u901a\u4fe1\u65b9\u5f0f\u6709\u54ea\u4e9b\uff1f\u6211\u88ab\u95ee\u5012\u4e86\uff01<\/p>\n<\/section>\n<\/section>\n
      \n
      \n
      \u9762\u8bd5\u5b98\uff1aTCP \u5982\u4f55\u4fdd\u8bc1\u4f20\u8f93\u7684\u53ef\u9760\u6027\uff1f<\/p>\n<\/section>\n<\/section>\n
      \n
      \n
      \u62dc\u6258\uff01\u5341\u4e2a\u9762\u8bd5\u5b98\u6709\u4e5d\u4e2a\u90fd\u8981\u95ee\u7f13\u5b58\u7a7f\u900f\u3001\u7f13\u5b58\u51fb\u7a7f\u3001\u7f13\u5b58\u96ea\u5d29<\/p>\n<\/section>\n<\/section>\n
      \n
      \n
      \u9762\u8bd5\u5b98\uff1afail-fast \u673a\u5236\u4e86\u89e3\u5417\uff1f\u4f60\u8fd9\u6837\u4f7f\u7528\u96c6\u5408\u4e0d\u4f1a\u6709\u95ee\u9898\u5417\uff1f\u3002\u3002<\/p>\n<\/section>\n<\/section>\n
      \n
      \n
      \u9762\u8bd5\u5b98\uff1aMySQL \u5355\u8868\u4e3a\u4ec0\u4e48\u4e0d\u8981\u8d85\u8fc7 2000W \u884c\uff1f\u3002\u3002<\/p>\n<\/section>\n<\/section>\n<\/section>\n<\/section>\n<\/section>\n
      \n
      \u672c\u7bc7\u6587\u7ae0\u6765\u6e90\u4e8e\u5fae\u4fe1\u516c\u4f17\u53f7: \u9762\u8bd5\u9e2d<\/p><\/blockquote>\n<\/li>\n<\/ul>\n<\/section>\n<\/div>\n","raw":"","protected":false},"excerpt":{"rendered":"
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