{"id":199652,"date":"2025-05-06T10:48:10","date_gmt":"2025-05-06T02:48:10","guid":{"rendered":"https:\/\/server.hk\/cnblog\/199652\/"},"modified":"2025-05-06T10:48:10","modified_gmt":"2025-05-06T02:48:10","slug":"%e4%bd%bf%e7%94%a8mysql%e4%b8%ad%e7%9a%84explain%e8%bf%9b%e8%a1%8c%e6%9f%a5%e8%af%a2%e4%bc%98%e5%8c%96","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/199652\/","title":{"rendered":"\u4f7f\u7528MySQL\u4e2d\u7684EXPLAIN\u8fdb\u884c\u67e5\u8be2\u4f18\u5316"},"content":{"rendered":"

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

\u4f7f\u7528MySQL\u4e2d\u7684EXPLAIN\u8fdb\u884c\u67e5\u8be2\u4f18\u5316<\/h1>\n

\u600e\u4e48\u5165\u95e8\u6570\u636e\u5e93\u7f16\u7a0b\uff1f\u9700\u8981\u5b66\u4e60\u54ea\u4e9b\u77e5\u8bc6\u70b9\uff1f\u8fd9\u662f\u65b0\u624b\u4eec\u521a\u63a5\u89e6\u7f16\u7a0b\u65f6\u5e38\u89c1\u7684\u95ee\u9898\uff1b\u4e0b\u9762\u4e3b\u673a\u5b9d\u8d1d\u5c31\u6765\u7ed9\u5927\u5bb6\u6574\u7406\u5206\u4eab\u4e00\u4e9b\u77e5\u8bc6\u70b9\uff0c\u5e0c\u671b\u80fd\u591f\u7ed9\u521d\u5b66\u8005\u4e00\u4e9b\u5e2e\u52a9\u3002\u672c\u7bc7\u6587\u7ae0\u5c31\u6765\u4ecb\u7ecd\u300a\u4f7f\u7528MySQL\u4e2d\u7684EXPLAIN\u8fdb\u884c\u67e5\u8be2\u4f18\u5316\u300b\uff0c\u6d89\u53ca\u5230\uff0c\u6709\u9700\u8981\u7684\u53ef\u4ee5\u6536\u85cf\u4e00\u4e0b<\/p>\n

MySQL\u4e2dEXPLAIN<\/code>\u7684\u7528\u6cd5\u53ca\u5177\u4f53\u4ee3\u7801\u793a\u4f8b<\/p>\n

\u4e00\u3001\u4ecb\u7ecd<\/h3>\n

\u5728MySQL\u4e2d\uff0cEXPLAIN<\/code>\u662f\u4e00\u4e2a\u5f88\u6709\u7528\u7684\u5de5\u5177\uff0c\u7528\u4e8e\u5206\u6790\u67e5\u8be2\u8bed\u53e5\u7684\u6267\u884c\u8ba1\u5212\u3002\u5b83\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u4e86\u89e3MySQL\u662f\u5982\u4f55\u5904\u7406\u67e5\u8be2\uff0c\u4ee5\u53ca\u5bf9\u67e5\u8be2\u6027\u80fd\u8fdb\u884c\u4f18\u5316\u63d0\u4f9b\u4e86\u91cd\u8981\u7684\u53c2\u8003\u3002<\/p>\n

\u4e8c\u3001\u4f7f\u7528\u65b9\u6cd5<\/h3>\n

\u8981\u4f7f\u7528EXPLAIN<\/code>\u8fdb\u884c\u67e5\u8be2\u5206\u6790\uff0c\u53ea\u9700\u8981\u5c06\u8981\u5206\u6790\u7684\u67e5\u8be2\u8bed\u53e5\u653e\u5728EXPLAIN<\/code>\u5173\u952e\u5b57\u4e4b\u540e\uff0c\u4f8b\u5982\uff1a<\/p>\n

EXPLAIN SELECT * FROM users WHERE age > 18;<\/pre>\n
\u4e09\u3001\u89e3\u8bfb\u7ed3\u679c<\/h3>\n
EXPLAIN<\/code>\u7684\u5206\u6790\u7ed3\u679c\u4ee5\u8868\u683c\u7684\u5f62\u5f0f\u5448\u73b0\uff0c\u5305\u542b\u4e86\u4e00\u4e9b\u5217\uff0c\u4e3b\u8981\u5305\u62ec\u4ee5\u4e0b\u51e0\u4e2a\u5b57\u6bb5\uff1a<\/p>\n
    \n
  1. id<\/code>\uff1a\u8868\u793a\u67e5\u8be2\u5e8f\u53f7\uff0c\u5982\u679c\u67e5\u8be2\u6709\u5d4c\u5957\uff0c\u5219\u76f8\u5bf9\u5e94\u5d4c\u5957\u5c42\u7ea7\u7684id\u4e5f\u4f1a\u9012\u589e\u3002<\/li>\n
  2. select_type<\/code>\uff1a\u8868\u793a\u67e5\u8be2\u7684\u7c7b\u578b\uff0c\u5305\u62ec\u7b80\u5355\u67e5\u8be2\u3001\u8054\u5408\u67e5\u8be2\u3001\u5b50\u67e5\u8be2\u7b49\u3002<\/li>\n
  3. table<\/code>\uff1a\u8868\u793a\u8fd9\u4e00\u884c\u7684\u6570\u636e\u662f\u5173\u8054\u7684\u54ea\u4e2a\u8868\u3002<\/li>\n
  4. type<\/code>\uff1a\u8868\u793a\u8bbf\u95ee\u8868\u7684\u65b9\u5f0f\uff0c\u5305\u62ec\u5168\u8868\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u3001\u8303\u56f4\u626b\u63cf\u7b49\u3002<\/li>\n
  5. possible_keys<\/code>\uff1a\u8868\u793a\u53ef\u80fd\u4f7f\u7528\u5230\u7684\u7d22\u5f15\u3002<\/li>\n
  6. key<\/code>\uff1a\u8868\u793a\u5b9e\u9645\u4f7f\u7528\u5230\u7684\u7d22\u5f15\u3002<\/li>\n
  7. key_len<\/code>\uff1a\u8868\u793a\u7d22\u5f15\u5b57\u6bb5\u7684\u957f\u5ea6\u3002<\/li>\n
  8. ref<\/code>\uff1a\u8868\u793a\u53c2\u8003\u7684\u5e38\u91cf\u6216\u5217\u3002<\/li>\n
  9. rows<\/code>\uff1a\u8868\u793a\u626b\u63cf\u7684\u884c\u6570\u3002<\/li>\n
  10. Extra<\/code>\uff1a\u8868\u793a\u5176\u4ed6\u4fe1\u606f\uff0c\u4f8b\u5982\u4f7f\u7528\u4e34\u65f6\u8868\u3001\u6587\u4ef6\u6392\u5e8f\u7b49\u3002<\/li>\n<\/ol>\n
    \u56db\u3001\u4f18\u5316\u5206\u6790<\/h3>\n
    \u901a\u8fc7\u5bf9\u89e3\u8bfb\u7ed3\u679c\u7684\u5206\u6790\uff0c\u6211\u4eec\u53ef\u4ee5\u8fdb\u884c\u6027\u80fd\u4f18\u5316\uff0c\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u89c1\u7684\u4f18\u5316\u6848\u4f8b\uff1a<\/p>\n
      \n
    1. \u7d22\u5f15\u4f18\u5316\uff1a\u901a\u8fc7\u5206\u6790possible_keys<\/code>\u548ckey<\/code>\u5b57\u6bb5\uff0c\u5224\u65ad\u662f\u5426\u4f7f\u7528\u4e86\u9002\u5f53\u7684\u7d22\u5f15\u3002\u5982\u679ckey<\/code>\u662fNULL<\/code>\uff0c\u5219\u8bf4\u660e\u6ca1\u6709\u4f7f\u7528\u7d22\u5f15\uff0c\u9700\u8981\u8003\u8651\u521b\u5efa\u7d22\u5f15\u4f18\u5316\u67e5\u8be2\u3002<\/li>\n
    2. \u626b\u63cf\u884c\u6570\u4f18\u5316\uff1a\u901a\u8fc7\u5206\u6790rows<\/code>\u5b57\u6bb5\uff0c\u5224\u65ad\u67e5\u8be2\u626b\u63cf\u7684\u884c\u6570\u662f\u5426\u8fc7\u591a\u3002\u5982\u679c\u626b\u63cf\u884c\u6570\u8f83\u5927\uff0c\u53ef\u4ee5\u8003\u8651\u5bf9\u67e5\u8be2\u8fdb\u884c\u91cd\u5199\uff0c\u51cf\u5c11\u626b\u63cf\u884c\u6570\u3002<\/li>\n
    3. \u67e5\u8be2\u7c7b\u578b\u4f18\u5316\uff1a\u901a\u8fc7\u5206\u6790select_type<\/code>\u5b57\u6bb5\uff0c\u5224\u65ad\u67e5\u8be2\u7684\u7c7b\u578b\u3002\u4f8b\u5982\uff0c\u5982\u679c\u67e5\u8be2\u662f\u5b50\u67e5\u8be2\uff0c\u53ef\u80fd\u9700\u8981\u8003\u8651\u4f7f\u7528JOIN\u6765\u66ff\u4ee3\u5b50\u67e5\u8be2\uff0c\u4ee5\u63d0\u9ad8\u67e5\u8be2\u6027\u80fd\u3002<\/li>\n
    4. \u8868\u5173\u8054\u4f18\u5316\uff1a\u901a\u8fc7\u5206\u6790table<\/code>\u5b57\u6bb5\uff0c\u5224\u65ad\u662f\u5426\u6709\u591a\u8868\u5173\u8054\uff0c\u662f\u5426\u9700\u8981\u8c03\u6574\u8868\u5173\u8054\u7684\u987a\u5e8f\uff0c\u51cf\u5c11\u4e34\u65f6\u8868\u7684\u4f7f\u7528\u3002<\/li>\n<\/ol>\n
      \u4e94\u3001\u793a\u4f8b\u4ee3\u7801<\/h3>\n
      \u4ee5\u4e0b\u662f\u4e00\u4e2a\u793a\u4f8b\u4ee3\u7801\uff0c\u6765\u8bf4\u660e\u5982\u4f55\u4f7f\u7528EXPLAIN<\/code>\uff1a<\/p>\n
      EXPLAIN SELECT * FROM orders WHERE customer_id = 100;<\/pre>\n
      \u6267\u884c\u4ee5\u4e0a\u4ee3\u7801\uff0c\u53ef\u4ee5\u5f97\u5230\u7c7b\u4f3c\u7684\u7ed3\u679c\uff1a<\/p>\n
      +----+-------------+--------+-------+---------------+------+---------+------+------+-------+\n| id | select_type | table  | type  | possible_keys | key  | key_len | ref  | rows | Extra |\n+----+-------------+--------+-------+---------------+------+---------+------+------+-------+\n|  1 | SIMPLE      | orders | const | customer_id   | id   | 4       | const|1     | NULL  |\n+----+-------------+--------+-------+---------------+------+---------+------+------+-------+<\/pre>\n
      \u901a\u8fc7\u89c2\u5bdf\u8fd9\u4e2a\u7ed3\u679c\uff0c\u6211\u4eec\u53ef\u4ee5\u5f97\u5230\u4ee5\u4e0b\u4fe1\u606f\uff1a<\/p>\n
        \n
      • \u67e5\u8be2\u662f\u4e00\u4e2a\u7b80\u5355\u67e5\u8be2\uff08SIMPLE\uff09\u3002<\/li>\n
      • \u67e5\u8be2\u4f7f\u7528\u4e86customer_id\u7d22\u5f15\u3002<\/li>\n
      • \u67e5\u8be2\u626b\u63cf\u7684\u884c\u6570\u662f1\u3002<\/li>\n<\/ul>\n
        \u901a\u8fc7\u8fd9\u4e9b\u4fe1\u606f\uff0c\u53ef\u4ee5\u5224\u65ad\u8fd9\u4e2a\u67e5\u8be2\u6027\u80fd\u8f83\u597d\uff0c\u56e0\u4e3a\u4f7f\u7528\u4e86\u7d22\u5f15\u4e14\u53ea\u626b\u63cf\u4e86\u4e00\u884c\u3002<\/p>\n
        \u516d\u3001\u603b\u7ed3<\/h3>\n
        \u901a\u8fc7\u4f7f\u7528EXPLAIN<\/code>\uff0c\u6211\u4eec\u53ef\u4ee5\u5206\u6790\u67e5\u8be2\u8bed\u53e5\u7684\u6267\u884c\u8ba1\u5212\uff0c\u4ece\u800c\u8fdb\u884c\u6027\u80fd\u4f18\u5316\u3002\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7\u5206\u6790\u67e5\u8be2\u7684\u7c7b\u578b\u3001\u7d22\u5f15\u4f7f\u7528\u60c5\u51b5\u3001\u626b\u63cf\u884c\u6570\u7b49\u4fe1\u606f\uff0c\u6765\u5224\u65ad\u67e5\u8be2\u662f\u5426\u9700\u8981\u8fdb\u884c\u4f18\u5316\uff0c\u5e76\u51b3\u5b9a\u91c7\u53d6\u54ea\u4e9b\u4f18\u5316\u7b56\u7565\u3002EXPLAIN<\/code>\u5728MySQL\u4f18\u5316\u4e2d\u662f\u4e00\u4e2a\u975e\u5e38\u91cd\u8981\u7684\u5de5\u5177\uff0c\u5e2e\u52a9\u6211\u4eec\u4e86\u89e3MySQL\u7684\u6267\u884c\u8ba1\u5212\uff0c\u63d0\u9ad8\u67e5\u8be2\u6027\u80fd\u3002<\/p>\n
        \u672c\u7bc7\u5173\u4e8e\u300a\u4f7f\u7528MySQL\u4e2d\u7684EXPLAIN\u8fdb\u884c\u67e5\u8be2\u4f18\u5316\u300b\u7684\u4ecb\u7ecd\u5c31\u5230\u6b64\u7ed3\u675f\u5566\uff0c\u4f46\u662f\u5b66\u65e0\u6b62\u5883\uff0c\u60f3\u8981\u4e86\u89e3\u5b66\u4e60\u66f4\u591a\u5173\u4e8e\u6570\u636e\u5e93\u7684\u76f8\u5173\u77e5\u8bc6\uff0c\u8bf7\u5173\u6ce8\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\uff01<\/p>\n
        \n
        \n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"
        \u4f7f\u7528MySQL\u4e2d\u7684EXPLAIN...<\/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-199652","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199652","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=199652"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199652\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=199652"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=199652"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=199652"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}