{"id":497,"date":"2024-11-04T22:33:24","date_gmt":"2024-11-04T14:33:24","guid":{"rendered":"http:\/\/www.wengdao.net\/?p=497"},"modified":"2024-11-05T00:01:01","modified_gmt":"2024-11-04T16:01:01","slug":"mysql-%e6%9f%a5%e4%b8%8b%e4%bc%98%e5%8c%96explain%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/jiandao.zliby.com\/?p=497","title":{"rendered":"Mysql \u67e5\u4e0b\u4f18\u5316EXPLAIN\u8be6\u89e3"},"content":{"rendered":"

\u4f8b\u5b50:<\/p>\n

EXPLAIN SELECT * FROM users WHERE age > 18;<\/code><\/pre>\n
EXPLAIN \u8f93\u51fa\u7684\u5217\u89e3\u6790
\n\u6bcf\u4e2a EXPLAIN \u7684\u8f93\u51fa\u7ed3\u679c\u5305\u542b\u5982\u4e0b\u5173\u952e\u5b57\u6bb5\uff1a<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
\u5217\u540d<\/th>\n\u8bf4\u660e<\/th>\n<\/tr>\n<\/thead>\n
id<\/td>\n\u67e5\u8be2\u4e2d\u6bcf\u4e2a SELECT \u5b50\u53e5\u7684\u6807\u8bc6\u7b26\u3002id \u8d8a\u5927\u4f18\u5148\u7ea7\u8d8a\u4f4e\uff0c\u6267\u884c\u987a\u5e8f\u662f\u4ece\u4e0a\u5230\u4e0b\u3002<\/td>\n<\/tr>\n
select_type<\/td>\nSELECT \u67e5\u8be2\u7c7b\u578b\uff0c\u8868\u793a\u662f\u7b80\u5355\u67e5\u8be2\u3001\u5b50\u67e5\u8be2\u3001\u8054\u5408\u67e5\u8be2\u8fd8\u662f\u6d3e\u751f\u8868\u7b49\u3002<\/td>\n<\/tr>\n
table<\/td>\n\u663e\u793a\u8be5\u884c\u5bf9\u5e94\u7684\u8868\u540d\uff0c\u8868\u793a\u67e5\u8be2\u6d89\u53ca\u5230\u7684\u8868\u3002<\/td>\n<\/tr>\n
partitions<\/td>\n\u4f7f\u7528\u7684\u5206\u533a\uff08\u4ec5\u5728\u8868\u6709\u5206\u533a\u65f6\u663e\u793a\uff09\u3002<\/td>\n<\/tr>\n
type<\/td>\n\u8fde\u63a5\u7c7b\u578b\uff0c\u663e\u793a\u8868\u7684\u8bbf\u95ee\u65b9\u5f0f\uff0c\u91cd\u8981\u7a0b\u5ea6\u4ece\u9ad8\u5230\u4f4e\u4f9d\u6b21\u662f system\u3001const\u3001eq_ref\u3001ref\u3001range \u7b49\u3002<\/td>\n<\/tr>\n
possible_keys<\/td>\n\u67e5\u8be2\u4e2d\u53ef\u80fd\u4f1a\u7528\u5230\u7684\u7d22\u5f15\u3002<\/td>\n<\/tr>\n
key<\/td>\n\u5b9e\u9645\u4f7f\u7528\u7684\u7d22\u5f15\u3002<\/td>\n<\/tr>\n
key_len<\/td>\n\u4f7f\u7528\u7684\u7d22\u5f15\u957f\u5ea6\uff0c\u8868\u793a MySQL \u4ece\u7d22\u5f15\u4e2d\u4f7f\u7528\u4e86\u591a\u5c11\u5b57\u8282\u3002<\/td>\n<\/tr>\n
ref<\/td>\n\u663e\u793a\u7d22\u5f15\u5217\u662f\u5426\u548c\u54ea\u4e9b\u5217\u6216\u5e38\u91cf\u8fdb\u884c\u6bd4\u8f83\u3002<\/td>\n<\/tr>\n
rows<\/td>\n\u9884\u4f30\u626b\u63cf\u7684\u884c\u6570\u3002\u8be5\u6570\u5b57\u8d8a\u5c0f\u8d8a\u597d\u3002<\/td>\n<\/tr>\n
filtered<\/td>\n\u8fc7\u6ee4\u6761\u4ef6\u7684\u767e\u5206\u6bd4\uff0c\u5373\u8fd4\u56de\u7684\u884c\u6570\u5360\u626b\u63cf\u884c\u6570\u7684\u767e\u5206\u6bd4\u3002<\/td>\n<\/tr>\n
Extra<\/td>\n\u663e\u793a\u6267\u884c\u8fc7\u7a0b\u4e2d\u989d\u5916\u7684\u4fe1\u606f\u3002<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\u5e38\u89c1\u7684 select_type \u503c<\/p>\n
    \n
  • SIMPLE\uff1a               \u7b80\u5355\u67e5\u8be2\uff0c\u67e5\u8be2\u4e2d\u4e0d\u5305\u542b\u5b50\u67e5\u8be2\u6216\u8054\u5408\u67e5\u8be2\u3002<\/li>\n
  • PRIMARY\uff1a          \u67e5\u8be2\u7684\u6700\u5916\u5c42\uff0c\u901a\u5e38\u662f\u4e3b\u67e5\u8be2\u3002<\/li>\n
  • SUBQUERY\uff1a         \u5b50\u67e5\u8be2\u3002<\/li>\n
  • DERIVED\uff1a          \u6d3e\u751f\u8868\uff08\u5b50\u67e5\u8be2\u5728 FROM \u5b50\u53e5\u4e2d\uff0cMySQL \u4f1a\u5c06\u5176\u89c6\u4e3a\u6d3e\u751f\u8868\uff09\u3002<\/li>\n
  • UNION\uff1a                \u8054\u5408\u67e5\u8be2\u7684\u4e00\u90e8\u5206\u3002<\/li>\n
  • DEPENDENT UNION\uff1a  \u8054\u5408\u67e5\u8be2\u7684\u4e00\u90e8\u5206\uff0c\u4f9d\u8d56\u4e8e\u5916\u90e8\u67e5\u8be2\u3002<\/li>\n<\/ul>\n
    \u5e38\u89c1\u7684 type \u503c\uff08\u8fde\u63a5\u7c7b\u578b\uff09, \u91cd\u8981\u7a0b\u5ea6\u4ece\u9ad8\u5230\u4f4e\u4f9d\u6b21\u4e3a\uff1a<\/p>\n
      \n
    • ALL\uff1a          \u5168\u8868\u626b\u63cf\uff0c\u6027\u80fd\u6700\u5dee\u3002<\/li>\n
    • index\uff1a            \u5168\u7d22\u5f15\u626b\u63cf\uff0c\u626b\u63cf\u6240\u6709\u7d22\u5f15\u9879\uff0c\u800c\u4e0d\u662f\u6570\u636e\u8868\u3002<\/li>\n
    • range\uff1a            \u8303\u56f4\u626b\u63cf\uff0c\u53ea\u626b\u63cf\u6307\u5b9a\u8303\u56f4\u7684\u7d22\u5f15\u9879\uff0c\u5e38\u7528\u4e8e BETWEEN\u3001>\u3001< \u7b49\u8303\u56f4\u6761\u4ef6\u3002<\/li>\n
    • ref\uff1a          \u975e\u552f\u4e00\u7d22\u5f15\u626b\u63cf\uff0c\u8fd4\u56de\u5339\u914d\u67d0\u4e00\u975e\u552f\u4e00\u503c\u7684\u6240\u6709\u884c\uff0c\u9002\u7528\u4e8e\u4e3b\u952e\u6216\u552f\u4e00\u7d22\u5f15\u4ee5\u5916\u7684\u7d22\u5f15\u3002<\/li>\n
    • eq_ref\uff1a           \u552f\u4e00\u7d22\u5f15\u626b\u63cf\uff0c\u8fd4\u56de\u5339\u914d\u552f\u4e00\u7d22\u5f15\u503c\u7684\u884c\uff0c\u901a\u5e38\u5728\u8fde\u63a5\u67e5\u8be2\u4e2d\u7528\u5230\u3002<\/li>\n
    • const\/system\uff1a  \u5f53\u67e5\u8be2\u6761\u4ef6\u80fd\u5339\u914d\u4e00\u4e2a\u552f\u4e00\u7d22\u5f15\u7684\u5355\u6761\u8bb0\u5f55\u65f6\u4f7f\u7528\uff0c\u901f\u5ea6\u6700\u5feb\u3002<\/li>\n<\/ul>\n
      Extra \u5b57\u6bb5\u5305\u542b\u4e86\u67e5\u8be2\u4f18\u5316\u5668\u5bf9\u67e5\u8be2\u8fdb\u884c\u7684\u5176\u4ed6\u64cd\u4f5c\uff0c\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u89c1\u7684\u503c\u53ca\u5176\u542b\u4e49\uff1a<\/p>\n
        \n
      • Using where\uff1a              \u8868\u793a MySQL \u4f1a\u5728\u5b58\u50a8\u5f15\u64ce\u8fd4\u56de\u6570\u636e\u540e\u8fdb\u884c\u8fc7\u6ee4\u3002<\/li>\n
      • Using index\uff1a              \u8868\u793a\u67e5\u8be2\u4ec5\u901a\u8fc7\u7d22\u5f15\u6ee1\u8db3\u8bf7\u6c42\uff0c\u4e0d\u9700\u8bbf\u95ee\u8868\u7684\u6570\u636e\u884c\uff0c\u6548\u7387\u9ad8\u3002<\/li>\n
      • Using filesort\uff1a               MySQL \u9700\u8981\u989d\u5916\u7684\u6392\u5e8f\u64cd\u4f5c\u3002ORDER BY \u65e0\u6cd5\u4f7f\u7528\u7d22\u5f15\u65f6\uff0cMySQL \u4f1a\u8fdb\u884c\u6587\u4ef6\u6392\u5e8f\uff0c\u6548\u7387\u8f83\u4f4e\u3002<\/li>\n
      • Using temporary\uff1a          \u67e5\u8be2\u8fc7\u7a0b\u4e2d\u4f7f\u7528\u4e86\u4e34\u65f6\u8868\uff0c\u901a\u5e38\u51fa\u73b0\u5728 GROUP BY\u3001ORDER BY \u7b49\u573a\u666f\uff0c\u6027\u80fd\u4f1a\u6709\u6240\u5f71\u54cd\u3002<\/li>\n
      • Using join buffer\uff1a            MySQL \u5728\u8fde\u63a5\u65f6\u4f7f\u7528\u4e86\u8fde\u63a5\u7f13\u5b58\uff0c\u901a\u5e38\u56e0\u4e3a\u8fde\u63a5\u6761\u4ef6\u4e2d\u7684\u5217\u6ca1\u6709\u7d22\u5f15\u3002<\/li>\n
      • Using where; Using index\uff1a \u901a\u8fc7\u7d22\u5f15\u5b8c\u6210\u6570\u636e\u67e5\u627e\u4e14\u65e0\u5168\u8868\u626b\u63cf\uff08\u8986\u76d6\u7d22\u5f15\uff09\u3002<\/li>\n<\/ul>\n
        \u4f8b\u5b50\uff1a<\/p>\n\n\n\n\n\n
        id<\/th>\nselect_type<\/th>\ntable<\/th>\ntype<\/th>\npossible_keys<\/th>\nkey<\/th>\nkey_len<\/th>\nref<\/th>\nrows<\/th>\nExtra<\/th>\n<\/tr>\n<\/thead>\n
        1<\/td>\nSIMPLE<\/td>\nusers<\/td>\nrange<\/td>\nage_index<\/td>\nage_index<\/td>\n4<\/td>\nNULL<\/td>\n1000<\/td>\nUsing where<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
        \u5206\u6790\uff1a
        \ntype \u4e3a range \u8868\u793a\u4f7f\u7528\u4e86\u8303\u56f4\u626b\u63cf\u3002
        \nkey  \u4f7f\u7528\u7684\u7d22\u5f15\u662f age_index
        \nrows \u4e3a 1000 \u8868\u793a\u9884\u4f30\u4f1a\u626b\u63cf 1000 \u884c\u6570\u636e\uff0c\u626b\u63cf\u884c\u6570\u8f83\u591a\uff0c\u67e5\u8be2\u901f\u5ea6\u53ef\u80fd\u8f83\u6162\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
        \u4f8b\u5b50: EXPLAIN SELECT * FROM users WHERE age > 18; EXPL […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/jiandao.zliby.com\/index.php?rest_route=\/wp\/v2\/posts\/497"}],"collection":[{"href":"https:\/\/jiandao.zliby.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jiandao.zliby.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jiandao.zliby.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jiandao.zliby.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=497"}],"version-history":[{"count":5,"href":"https:\/\/jiandao.zliby.com\/index.php?rest_route=\/wp\/v2\/posts\/497\/revisions"}],"predecessor-version":[{"id":503,"href":"https:\/\/jiandao.zliby.com\/index.php?rest_route=\/wp\/v2\/posts\/497\/revisions\/503"}],"wp:attachment":[{"href":"https:\/\/jiandao.zliby.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=497"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jiandao.zliby.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=497"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jiandao.zliby.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=497"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}