{"id":15,"date":"2025-06-04T16:47:21","date_gmt":"2025-06-04T08:47:21","guid":{"rendered":"https:\/\/www.shoubashou.com\/?p=15"},"modified":"2025-06-04T16:47:21","modified_gmt":"2025-06-04T08:47:21","slug":"10-%e5%88%86%e9%92%9f%e6%95%99%e4%bc%9a%e4%bd%a0%e5%a6%82%e4%bd%95%e7%9c%8b%e6%87%82-mysql-%e6%89%a7%e8%a1%8c%e8%ae%a1%e5%88%92","status":"publish","type":"post","link":"https:\/\/www.shoubashou.com\/?p=15","title":{"rendered":"10 \u5206\u949f\u6559\u4f1a\u4f60\u5982\u4f55\u770b\u61c2 MySQL \u6267\u884c\u8ba1\u5212"},"content":{"rendered":"\n

from \uff1a\u7a0b\u5e8f\u5458\u8001\u9a6c\u5934 https:\/\/blog.csdn.net\/weixin_74412978\/article\/details\/144772135<\/a><\/p>\n\n\n\n

\u901a\u5e38\u67e5\u8be2\u6162\u67e5\u8be2SQL\u8bed\u53e5\u65f6\u4f1a\u4f7f\u7528EXPLAIN\u547d\u4ee4\u6765\u67e5\u770bSQL\u8bed\u53e5\u7684\u6267\u884c\u8ba1\u5212\uff0c\u901a\u8fc7\u8fd4\u56de\u7684\u4fe1\u606f\uff0c\u53ef\u4ee5\u4e86\u89e3\u5230Mysql\u4f18\u5316\u5668\u662f\u5982\u4f55\u6267\u884cSQL\u8bed\u53e5\uff0c\u901a\u8fc7\u5206\u6790\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u63d0\u4f9b\u4f18\u5316\u7684\u601d\u8def\u3002<\/p>\n\n\n\n

1\u3001Explain \u4f5c\u7528<\/strong><\/h3>\n\n\n\n

explain \u547d\u4ee4\u4e3b\u8981\u7528\u4e8e\u67e5\u770b SQL \u8bed\u53e5\u7684\u6267\u884c\u8ba1\u5212\uff0c\u8be5\u547d\u4ee4\u53ef\u4ee5\u6a21\u62df\u4f18\u5316\u5668\u6267\u884c SQL \u67e5\u8be2\u8bed\u53e5\uff0c\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u7f16\u5199\u548c\u4f18\u5316 SQL\u3002\u90a3\u4e48 explain \u5177\u4f53\u53ef\u4ee5\u63d0\u4f9b\u54ea\u4e9b\u4fe1\u606f\uff0c\u5e2e\u52a9\u6211\u4eec\u5982\u4f55\u53bb\u4f18\u5316 SQl \u7684\u5462\uff1f<\/p>\n\n\n\n

1.1\u3001\u8868\u7684\u8bfb\u53d6\u987a\u5e8f<\/p>\n\n\n\n

1.2\u3001\u6570\u636e\u8bfb\u53d6\u64cd\u4f5c\u7684\u64cd\u4f5c\u7c7b\u578b<\/p>\n\n\n\n

1.3\u3001\u54ea\u4e9b\u7d22\u5f15\u53ef\u4ee5\u4f7f\u7528<\/p>\n\n\n\n

1.4\u3001\u54ea\u4e9b\u7d22\u5f15\u88ab\u5b9e\u9645\u4f7f\u7528<\/p>\n\n\n\n

1.5\u3001\u8868\u4e4b\u95f4\u7684\u5f15\u7528<\/p>\n\n\n\n

1.6\u3001\u6bcf\u5f20\u8868\u6709\u591a\u5c11\u884c\u88ab\u4f18\u5316\u5668\u67e5\u8be2<\/p>\n\n\n\n

2\u3001Explain \u5982\u4f55\u4f7f\u7528<\/strong><\/h3>\n\n\n\n

\u4f7f\u7528\u65b9\u5f0f\uff1a explain + \u5f85\u6267\u884c\u7684sql<\/p>\n\n\n\n

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

explain \u4f1a\u8fd4\u56de\u4e00\u4e2a\u5f85\u6267\u884c SQL \u7684\u6267\u884c\u8ba1\u5212\u5217\u8868\uff0c\u5217\u8868\u5305\u542b\u4e86 12 \u4e2a\u5b57\u6bb5\uff0c\u5b57\u6bb5\u5171\u540c\u63cf\u8ff0\u4e86 SQL \u5728\u6267\u884c\u8ba1\u5212\u4e2d\u5c06\u4f1a\u91c7\u53d6\u4f55\u79cd\u65b9\u5f0f\u6267\u884c\u3002\u4ee5\u4e0b\u5217\u8868\u8be6\u7ec6\u63cf\u8ff0\u4e86\u6267\u884c\u8ba1\u5212\u8868\u7684\u5b57\u6bb5\u542b\u4e49\uff1a<\/p>\n\n\n\n

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

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

3. \u5173\u952e\u5b57\u6bb5\u5206\u6790<\/h3>\n\n\n\n

<\/a>\uff081\uff09id<\/h4>\n\n\n\n

\u6267\u884c select \u8bed\u53e5\u67e5\u8be2\u7684\u5e8f\u5217\u53f7\uff0c\u5305\u542b\u4e00\u7ec4\u6570\u5b57\uff0c\u8868\u793a\u67e5\u8be2\u4e2d\u6267\u884c select \u5b50\u53e5\u6216\u64cd\u4f5c\u8868\u7684\u987a\u5e8f\uff0c\u5b83\u6709\u4e09\u79cd\u60c5\u51b5\uff1a<\/p>\n\n\n\n

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

\uff082\uff09select_type<\/h4>\n\n\n\n

\u5c31\u662f\u6570\u636e\u8bfb\u53d6\u64cd\u4f5c\u7684\u64cd\u4f5c\u7c7b\u578b\uff0c\u4ed6\u4e00\u5171\u6709\u4ee5\u4e0b\u51e0\u79cd\uff1a<\/p>\n\n\n\n

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

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

\uff083\uff09table<\/h4>\n\n\n\n

\u663e\u793a\u7684\u67e5\u8be2\u8868\u540d\uff0c\u5982\u679c\u67e5\u8be2\u4f7f\u7528\u4e86\u522b\u540d\uff0c\u90a3\u4e48\u8fd9\u91cc\u663e\u793a\u7684\u662f\u522b\u540d\uff0c\u5982\u679c\u4e0d\u6d89\u53ca\u5bf9\u6570\u636e\u8868\u7684\u64cd\u4f5c\uff0c\u90a3\u4e48\u8fd9\u663e\u793a\u4e3a null\uff0c\u4e5f\u53ef\u4ee5\u662f\u4ee5\u4e0b\u4e4b\u4e00\uff1a<\/p>\n\n\n\n

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

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

\uff084\uff09partitions<\/h4>\n\n\n\n

\u67e5\u8be2\u5c06\u5339\u914d\u8bb0\u5f55\u7684\u5206\u533a\u3002\u8be5\u503cNULL<\/code>\u7528\u4e8e\u975e\u5206\u533a\u8868\u3002<\/p>\n\n\n\n

<\/a>\uff085\uff09type<\/h4>\n\n\n\n

\u4f9d\u6b21\u4ece\u597d\u5230\u5dee\uff1a<\/p>\n\n\n\n

\n

system<\/code>>const<\/code>>eq_ref<\/code>>ref<\/code>>ref_or_null<\/code>>range<\/code>>index<\/code>>ALL<\/code><\/p>\n<\/blockquote>\n\n\n\n

\u9664\u4e86all<\/code>\u4e4b\u5916\uff0c\u5176\u4ed6\u7684type<\/code>\u90fd\u53ef\u4ee5\u4f7f\u7528\u5230\u7d22\u5f15\uff0c\u9664\u4e86index_merge<\/code>\u4e4b\u5916\uff0c\u5176\u4ed6\u7684type<\/code>\u53ea\u53ef\u4ee5\u7528\u5230\u4e00\u4e2a\u7d22\u5f15\u3002<\/p>\n\n\n\n

\u6211\u4eec\u81ea\u5df1\u521b\u5efa\u4e00\u7cfb\u5217\u8868\u6765\u5b9e\u9a8c\u4e0b\uff1a<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n
SET NAMES utf8mb4;\nSET FOREIGN_KEY_CHECKS = 0;\n \n-- ----------------------------\n-- Table structure for goods\n-- ----------------------------\nDROP TABLE IF EXISTS `goods`;\nCREATE TABLE `goods`  (\n  `id` int(11) NOT NULL,\n  `sn` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,\n  `name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,\n  PRIMARY KEY (`id`) USING BTREE\n) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci ROW_FORMAT = Dynamic;\n \n-- ----------------------------\n-- Records of goods\n-- ----------------------------\nINSERT INTO `goods` VALUES (1, 'sn123456', '\u8863\u670d');\n \n-- ----------------------------\n-- Table structure for sku\n-- ----------------------------\nDROP TABLE IF EXISTS `sku`;\nCREATE TABLE `sku`  (\n  `id` int(11) NOT NULL,\n  `goods_id` int(11) NOT NULL,\n  `status` int(11) NOT NULL,\n  `deleted` int(11) NOT NULL,\n  `barcode` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,\n  `name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,\n  PRIMARY KEY (`id`) USING BTREE,\n  UNIQUE INDEX `index_2`(`name`) USING BTREE,\n  INDEX `index_1`(`goods_id`, `status`, `deleted`, `barcode`) USING BTREE\n) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci ROW_FORMAT = Dynamic;\n \n-- ----------------------------\n-- Records of sku\n-- ----------------------------\nINSERT INTO `sku` VALUES (1, 1, 1, 0, 'kt123456', '\u9ed1\u8272');\n \nSET FOREIGN_KEY_CHECKS = 1;<\/code><\/pre>\n\n\n\n
<\/p>\n\n\n\n
system<\/h5>\n\n\n\n
\u8868\u53ea\u6709\u4e00\u884c\u8bb0\u5f55\uff08\u7b49\u4e8e\u7cfb\u7edf\u8868\uff09\uff0c\u8fd9\u662f const \u7c7b\u578b\u7684\u7279\u4f8b\uff0c\u5e73\u65f6\u4e0d\u4f1a\u51fa\u73b0\uff0c\u8fd9\u4e2a\u4e5f\u53ef\u5ffd\u7565\u4e0d\u8ba1\uff1b<\/p>\n\n\n\n
const<\/h5>\n\n\n\n
\u8868\u793a\u901a\u8fc7\u7d22\u5f15\u4e00\u6b21\u5c31\u627e\u5230\u4e86\uff0cconst \u7528\u4e8e\u6bd4\u8f83 primary key \u6216\u8005 unique \u7d22\u5f15\u3002\u56e0\u4e3a\u53ea\u5339\u914d\u4e00\u884c\u8bb0\u5f55\uff0c\u6240\u4ee5\u5f88\u5feb\u3002\u5982\u679c\u5c06\u4e3b\u952e\u7f6e\u4e8e where \u5217\u8868\u4e2d\uff0cmysql \u5c31\u80fd\u5c06\u8be5\u67e5\u8be2\u8f6c\u6362\u6210\u4e00\u4e2a\u5e38\u91cf\uff1b<\/p>\n\n\n\n
<\/code><\/pre>\n\n\n\n
\n
EXPLAIN SELECT * FROM sku WHERE id=1;<\/p>\n<\/blockquote>\n\n\n\n
\"\"<\/figure>\n\n\n\n
<\/p>\n\n\n\n
eq_ref<\/h5>\n\n\n\n
\u552f\u4e00\u6027\u7d22\u5f15\u626b\u63cf\uff0c\u5bf9\u4e8e\u6bcf\u4e00\u4e2a\u7d22\u5f15\u952e\uff0c\u8868\u4e2d\u53ea\u6709\u4e00\u6761\u8bb0\u5f55\u4e0e\u4e4b\u5339\u914d\uff0c\u5e38\u7528\u4e8e\u4e3b\u952e\u6216\u552f\u4e00\u7d22\u5f15\u626b\u63cf\uff1b\u6b64\u7c7b\u578b\u901a\u5e38\u51fa\u73b0\u5728\u591a\u8868\u7684 join \u7b49\u503c\u67e5\u8be2\uff0c\u8868\u793a\u5bf9\u4e8e\u524d\u8868\u7684\u6bcf\u4e00\u4e2a\u7ed3\u679c\uff0c\u90fd\u53ea\u80fd\u5339\u914d\u5230\u540e\u8868\u7684\u4e00\u884c\u7ed3\u679c\uff0c\u67e5\u8be2\u6548\u7387\u8f83\u9ad8\u3002<\/p>\n\n\n\n
\n
EXPLAIN SELECT * FROM sku,goods WHERE sku.goods_id=goods.id;<\/p>\n<\/blockquote>\n\n\n\n
\"\"<\/figure>\n\n\n\n
ref<\/h5>\n\n\n\n
\u975e\u552f\u4e00\u6027\u7d22\u5f15\u626b\u63cf\uff0c\u8fd4\u56de\u5339\u914d\u67d0\u4e2a\u5355\u72ec\u503c\u5f97\u6240\u6709\u884c\uff0c\u672c\u8d28\u4e0a\u4e5f\u662f\u4e00\u79cd\u7d22\u5f15\u8bbf\u95ee\uff0c\u5b83\u8fd4\u56de\u6240\u6709\u5339\u914d\u67d0\u4e2a\u5355\u72ec\u503c\u7684\u884c\uff0c\u7136\u800c\uff0c\u5b83\u53ef\u80fd\u4f1a\u627e\u5230\u591a\u4e2a\u7b26\u5408\u6761\u4ef6\u7684\u884c\uff0c\u6240\u4ee5\u5b83\u5e94\u8be5\u5c5e\u4e8e\u67e5\u627e\u548c\u626b\u63cf\u7684\u6df7\u5408\u4f53\uff1b<\/p>\n\n\n\n
\n
EXPLAIN SELECT * FROM sku WHERE goods_id=1;<\/p>\n<\/blockquote>\n\n\n\n
\"\"<\/figure>\n\n\n\n
<\/p>\n\n\n\n
ref_or_null<\/h5>\n\n\n\n
\u4e8c\u7ea7\u7d22\u5f15\u7b49\u503c\u6bd4\u8f83\u540c\u65f6\u9650\u5b9a is null \u3002<\/p>\n\n\n\n
\n
EXPLAIN SELECT * FROM sku WHERE name=’123456′ or name IS NULL;<\/p>\n<\/blockquote>\n\n\n\n
\"\"<\/figure>\n\n\n\n
<\/p>\n\n\n\n
range<\/h5>\n\n\n\n
\u53ea\u68c0\u7d22\u7ed9\u5b9a\u8303\u56f4\u7684\u884c\uff0c\u4f7f\u7528\u4e00\u4e2a\u7d22\u5f15\u6765\u9009\u62e9\u884c\uff0ckey\u5217\u663e\u793a\u4f7f\u7528\u54ea\u4e2a\u7d22\u5f15\uff0c\u4e00\u822c\u5c31\u662f\u5728\u4f60\u7684 where \u8bed\u53e5\u4e2d\u51fa\u73b0\u4e86 between\u3001<\u3001>\u3001in \u7b49\u7684\u67e5\u8be2\uff1b\u8fd9\u79cd\u8303\u56f4\u7d22\u5f15\u626b\u63cf\u6bd4\u5168\u8868\u626b\u63cf\u8981\u597d\uff0c\u56e0\u4e3a\u5b83\u53ea\u9700\u8981\u5f00\u59cb\u4e8e\u7d22\u5f15\u7684\u67d0\u4e00\u4e2a\u70b9\uff0c\u7ed3\u675f\u4e8e\u53e6\u4e00\u4e2a\u70b9\uff0c\u4e0d\u7528\u626b\u63cf\u5168\u90e8\u7d22\u5f15\uff1b<\/p>\n\n\n\n
\n
EXPLAIN SELECT * FROM sku WHERE id BETWEEN 1 and 10;<\/p>\n<\/blockquote>\n\n\n\n
\"\"<\/figure>\n\n\n\n
index<\/h5>\n\n\n\n
index \u548c all \u533a\u522b\u4e3a index \u7c7b\u578b\u53ea\u904d\u5386\u7d22\u5f15\u6811\uff0c\u8fd9\u901a\u5e38\u6bd4 all \u5feb\uff0c\u56e0\u4e3a\u7d22\u5f15\u6587\u4ef6\u901a\u5e38\u6bd4\u6570\u636e\u6587\u4ef6\u5c0f\uff1b\u4e5f\u5c31\u662f\u8bf4\u867d\u7136 all \u548c index \u90fd\u662f\u8bfb\u5199\u8868\uff0c\u4f46 index \u662f\u4ece\u7d22\u5f15\u4e2d\u8bfb\u53d6\u7684\uff0c\u800c all \u662f\u4ece\u786c\u76d8\u4e2d\u8bfb\u7684\uff1b<\/p>\n\n\n\n
EXPLAIN SELECT barcode FROM sku WHERE deleted=0;<\/code><\/pre>\n\n\n\n
\"\"<\/figure>\n\n\n\n
all<\/h5>\n\n\n\n
\u4e5f\u5c31\u662f\u5168\u8868\u626b\u63cf\uff1b<\/p>\n\n\n\n
EXPLAIN SELECT * FROM sku WHERE deleted=0;<\/code><\/pre>\n\n\n\n
\"\"<\/figure>\n\n\n\n
<\/p>\n\n\n\n
\uff086\uff09possible_keys<\/h4>\n\n\n\n
\u67e5\u8be2\u53ef\u80fd\u4f7f\u7528\u5230\u7684\u7d22\u5f15\u90fd\u4f1a\u5728\u8fd9\u91cc\u5217\u51fa\u6765\u3002<\/p>\n\n\n\n
\uff087\uff09key<\/h4>\n\n\n\n
\u67e5\u8be2\u771f\u6b63\u4f7f\u7528\u5230\u7684\u7d22\u5f15\uff0cselect_type\u4e3aindex_merge\u65f6\uff0c\u8fd9\u91cc\u53ef\u80fd\u51fa\u73b0\u4e24\u4e2a\u4ee5\u4e0a\u7684\u7d22\u5f15\uff0c\u5176\u4ed6\u7684select_type\u8fd9\u91cc\u53ea\u4f1a\u51fa\u73b0\u4e00\u4e2a\u3002<\/p>\n\n\n\n
\uff088\uff09key_len<\/h4>\n\n\n\n
key_len \u8868\u793a\u8be5\u5217\u8ba1\u7b97\u67e5\u8be2\u4e2d\u4f7f\u7528\u7684\u7d22\u5f15\u7684\u957f\u5ea6\u3002\u4f8b\u5982\uff1aSELECT * FROM table where age = 1 and name like ‘xx’\uff0c\u5047\u8bbe age \u662f int \u7c7b\u578b\u4e14\u4e0d\u53ef\u4e3a null\uff1bname \u662f varchar(20) \u7c7b\u578b\u4e14\u53ef\u4ee5\u4e3a null\uff0c\u7f16\u7801\u4e3a utf8\u3002\u82e5\u4ee5\u8fd9\u4e24\u4e2a\u5b57\u6bb5\u4e3a\u7d22\u5f15\u67e5\u8be2\uff0c\u90a3\u4e48 key_len \u7684\u503c\u4e3a 4 + 3 * 20 + 2 + 1 = 67\u3002\u5177\u4f53\u8ba1\u7b97\u89c4\u5219\u5982\u4e0b\u8868\u6240\u793a\uff1a<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\uff089\uff09ref<\/h4>\n\n\n\n
\u5982\u679c\u662f\u4f7f\u7528\u7684\u5e38\u6570\u7b49\u503c\u67e5\u8be2\uff0c\u8fd9\u91cc\u4f1a\u663e\u793aconst\uff0c\u5982\u679c\u662f\u8fde\u63a5\u67e5\u8be2\uff0c\u88ab\u9a71\u52a8\u8868\u7684\u6267\u884c\u8ba1\u5212\u8fd9\u91cc\u4f1a\u663e\u793a\u9a71\u52a8\u8868\u7684\u5173\u8054\u5b57\u6bb5\uff0c\u5982\u679c\u662f\u6761\u4ef6\u4f7f\u7528\u4e86\u8868\u8fbe\u5f0f\u6216\u8005\u51fd\u6570\uff0c\u6216\u8005\u6761\u4ef6\u5217\u53d1\u751f\u4e86\u5185\u90e8\u9690\u5f0f\u8f6c\u6362\uff0c\u8fd9\u91cc\u53ef\u80fd\u663e\u793a\u4e3afunc\u3002<\/p>\n\n\n\n
\uff0810\uff09rows<\/h4>\n\n\n\n
\u8fd9\u91cc\u662f\u6267\u884c\u8ba1\u5212\u4e2d\u4f30\u7b97\u7684\u626b\u63cf\u884c\u6570\uff0c\u4e0d\u662f\u7cbe\u786e\u503c\u3002<\/p>\n\n\n\n
\uff0811\uff09filtered<\/h4>\n\n\n\n
\u4f7f\u7528explain extended\u65f6\u4f1a\u51fa\u73b0\u8fd9\u4e2a\u5217\uff0c5.7\u4e4b\u540e\u7684\u7248\u672c\u9ed8\u8ba4\u5c31\u6709\u8fd9\u4e2a\u5b57\u6bb5\uff0c\u4e0d\u9700\u8981\u4f7f\u7528explain extended\u4e86\u3002\u8fd9\u4e2a\u5b57\u6bb5\u8868\u793a\u5b58\u50a8\u5f15\u64ce\u8fd4\u56de\u7684\u6570\u636e\u5728server\u5c42\u8fc7\u6ee4\u540e\uff0c\u5269\u4e0b\u591a\u5c11\u6ee1\u8db3\u67e5\u8be2\u7684\u8bb0\u5f55\u6570\u91cf\u7684\u6bd4\u4f8b\uff0c\u6ce8\u610f\u662f\u767e\u5206\u6bd4\uff0c\u4e0d\u662f\u5177\u4f53\u8bb0\u5f55\u6570\u3002<\/p>\n\n\n\n
\uff0812\uff09Extra<\/h4>\n\n\n\n
\u8fd9\u4e2a\u5217\u53ef\u4ee5\u663e\u793a\u7684\u4fe1\u606f\u975e\u5e38\u591a\uff0c\u6709\u51e0\u5341\u79cd\uff0c\u5e38\u7528\u7684\u6709\uff1a<\/p>\n\n\n\n
1\u3001distinct\uff1a\u5728select\u90e8\u5206\u4f7f\u7528\u4e86distinct\u5173\u952e\u5b57<\/p>\n\n\n\n
2\u3001no tables used\uff1a\u4e0d\u5e26from\u5b57\u53e5\u7684\u67e5\u8be2\u6216\u8005From dual\u67e5\u8be2\u3002\u4f7f\u7528not in()\u5f62\u5f0f\u5b50\u67e5\u8be2\u6216not exists()\u8fd0\u7b97\u7b26\u7684\u8fde\u63a5\u67e5\u8be2\uff0c\u8fd9\u79cd\u53eb\u505a\u53cd\u8fde\u63a5\u3002\u5373\uff0c\u4e00\u822c\u8fde\u63a5\u67e5\u8be2\u662f\u5148\u67e5\u8be2\u5185\u8868\uff0c\u518d\u67e5\u8be2\u5916\u8868\uff0c\u53cd\u8fde\u63a5\u5c31\u662f\u5148\u67e5\u8be2\u5916\u8868\uff0c\u518d\u67e5\u8be2\u5185\u8868\u3002<\/p>\n\n\n\n
3\u3001using filesort\uff1a\u8bf4\u660emysql\u4f1a\u5bf9\u6570\u636e\u4f7f\u7528\u4e00\u4e2a\u5916\u90e8\u7684\u7d22\u5f15\u6392\u5e8f\uff0c\u800c\u4e0d\u662f\u6309\u7167\u8868\u5185\u7684\u7d22\u5f15\u987a\u5e8f\u8fdb\u884c\u8bfb\u53d6\u3002mysql\u4e2d\u65e0\u6cd5\u5229\u7528\u7d22\u5f15\u5b8c\u6210\u7684\u6392\u5e8f\u64cd\u4f5c\u79f0\u4e3a\u201c\u6587\u4ef6\u6392\u5e8f\u201d\u3002\u6392\u5e8f\u65f6\u65e0\u6cd5\u4f7f\u7528\u5230\u7d22\u5f15\u65f6\uff0c\u5c31\u4f1a\u51fa\u73b0\u8fd9\u4e2a\u3002\u5e38\u89c1\u4e8eorder by\u8bed\u53e5\u4e2d\uff0c\u9700\u8981\u5c3d\u5feb\u4f18\u5316<\/p>\n\n\n\n
4\u3001using index\uff1a\u67e5\u8be2\u65f6\u4e0d\u9700\u8981\u56de\u8868\u67e5\u8be2\uff0c\u76f4\u63a5\u901a\u8fc7\u7d22\u5f15\u5c31\u53ef\u4ee5\u83b7\u53d6\u67e5\u8be2\u7684\u6570\u636e\u3002<\/p>\n\n\n\n
5\u3001using join buffer\uff08block nested loop\uff09\uff0cusing join buffer\uff08batched key accss\uff09 \uff1a5.6.x\u4e4b\u540e\u7684\u7248\u672c\u4f18\u5316\u5173\u8054\u67e5\u8be2\u7684BNL\uff0cBKA\u7279\u6027\u3002\u4e3b\u8981\u662f\u51cf\u5c11\u5185\u8868\u7684\u5faa\u73af\u6570\u91cf\u4ee5\u53ca\u6bd4\u8f83\u987a\u5e8f\u5730\u626b\u63cf\u67e5\u8be2\u3002<\/p>\n\n\n\n
6\u3001using sort_union\uff0cusing_union\uff0cusing intersect\uff0cusing sort_intersection\uff1a<\/p>\n\n\n\n
using intersect\uff1a\u8868\u793a\u4f7f\u7528and\u7684\u5404\u4e2a\u7d22\u5f15\u7684\u6761\u4ef6\u65f6\uff0c\u8be5\u4fe1\u606f\u8868\u793a\u662f\u4ece\u5904\u7406\u7ed3\u679c\u83b7\u53d6\u4ea4\u96c6<\/p>\n\n\n\n
using union\uff1a\u8868\u793a\u4f7f\u7528or\u8fde\u63a5\u5404\u4e2a\u4f7f\u7528\u7d22\u5f15\u7684\u6761\u4ef6\u65f6\uff0c\u8be5\u4fe1\u606f\u8868\u793a\u4ece\u5904\u7406\u7ed3\u679c\u83b7\u53d6\u5e76\u96c6<\/p>\n\n\n\n
using sort_union\u548cusing sort_intersection\uff1a\u4e0e\u524d\u9762\u4e24\u4e2a\u5bf9\u5e94\u7684\u7c7b\u4f3c\uff0c\u53ea\u662f\u4ed6\u4eec\u662f\u51fa\u73b0\u5728\u7528and\u548cor\u67e5\u8be2\u4fe1\u606f\u91cf\u5927\u65f6\uff0c\u5148\u67e5\u8be2\u4e3b\u952e\uff0c\u7136\u540e\u8fdb\u884c\u6392\u5e8f\u5408\u5e76\u540e\uff0c\u624d\u80fd\u8bfb\u53d6\u8bb0\u5f55\u5e76\u8fd4\u56de\u3002<\/p>\n\n\n\n
using temporary\uff1a\u8868\u793a\u4f7f\u7528\u4e86\u4e34\u65f6\u8868\u5b58\u50a8\u4e2d\u95f4\u7ed3\u679c\u3002\u4e34\u65f6\u8868\u53ef\u4ee5\u662f\u5185\u5b58\u4e34\u65f6\u8868\u548c\u78c1\u76d8\u4e34\u65f6\u8868\uff0c\u6267\u884c\u8ba1\u5212\u4e2d\u770b\u4e0d\u51fa\u6765\uff0c\u9700\u8981\u67e5\u770bstatus\u53d8\u91cf\uff0cused_tmp_table\uff0cused_tmp_disk_table\u624d\u80fd\u770b\u51fa\u6765\u3002\u5e38\u89c1\u4e8eorder by\u548c\u5206\u7ec4\u67e5\u8be2group by\u3002group by\u4e00\u5b9a\u8981\u9075\u5faa\u6240\u5efa\u7d22\u5f15\u7684\u987a\u5e8f\u4e0e\u4e2a\u6570\u3002\u9700\u8981\u5c3d\u5feb\u4f18\u5316<\/p>\n\n\n\n
using where\uff1a\u8868\u793a\u5b58\u50a8\u5f15\u64ce\u8fd4\u56de\u7684\u8bb0\u5f55\u5e76\u4e0d\u662f\u6240\u6709\u7684\u90fd\u6ee1\u8db3\u67e5\u8be2\u6761\u4ef6\uff0c\u9700\u8981\u5728server\u5c42\u8fdb\u884c\u8fc7\u6ee4\u3002\u67e5\u8be2\u6761\u4ef6\u4e2d\u5206\u4e3a\u9650\u5236\u6761\u4ef6\u548c\u68c0\u67e5\u6761\u4ef6\uff0c5.6\u4e4b\u524d\uff0c\u5b58\u50a8\u5f15\u64ce\u53ea\u80fd\u6839\u636e\u9650\u5236\u6761\u4ef6\u626b\u63cf\u6570\u636e\u5e76\u8fd4\u56de\uff0c\u7136\u540eserver\u5c42\u6839\u636e\u68c0\u67e5\u6761\u4ef6\u8fdb\u884c\u8fc7\u6ee4\u518d\u8fd4\u56de\u771f\u6b63\u7b26\u5408\u67e5\u8be2\u7684\u6570\u636e\u30025.6.x\u4e4b\u540e\u652f\u6301ICP\u7279\u6027(index condition pushdown\uff0c\u7d22\u5f15\u4e0b\u63a8)\uff0c\u53ef\u4ee5\u628a\u68c0\u67e5\u6761\u4ef6\u4e5f\u4e0b\u63a8\u5230\u5b58\u50a8\u5f15\u64ce\u5c42\uff0c\u4e0d\u7b26\u5408\u68c0\u67e5\u6761\u4ef6\u548c\u9650\u5236\u6761\u4ef6\u7684\u6570\u636e\uff0c\u76f4\u63a5\u4e0d\u8bfb\u53d6\uff0c\u8fd9\u6837\u5c31\u5927\u5927\u51cf\u5c11\u4e86\u5b58\u50a8\u5f15\u64ce\u626b\u63cf\u7684\u8bb0\u5f55\u6570\u91cf\u3002extra\u5217\u663e\u793ausing index condition<\/p>\n\n\n\n
firstmatch(tb_name) \uff1a5.6.x\u5f00\u59cb\u5f15\u5165\u7684\u4f18\u5316\u5b50\u67e5\u8be2\u7684\u65b0\u7279\u6027\u4e4b\u4e00\uff0c\u5e38\u89c1\u4e8ewhere\u5b57\u53e5\u542b\u6709in()\u7c7b\u578b\u7684\u5b50\u67e5\u8be2\u3002\u5982\u679c\u5185\u8868\u7684\u6570\u636e\u91cf\u6bd4\u8f83\u5927\uff0c\u5c31\u53ef\u80fd\u51fa\u73b0\u8fd9\u4e2a<\/p>\n\n\n\n
loosescan(m..n) \uff1a5.6.x\u4e4b\u540e\u5f15\u5165\u7684\u4f18\u5316\u5b50\u67e5\u8be2\u7684\u65b0\u7279\u6027\u4e4b\u4e00\uff0c\u5728in()\u7c7b\u578b\u7684\u5b50\u67e5\u8be2\u4e2d\uff0c\u5b50\u67e5\u8be2\u8fd4\u56de\u7684\u53ef\u80fd\u6709\u91cd\u590d\u8bb0\u5f55\u65f6\uff0c\u5c31\u53ef\u80fd\u51fa\u73b0\u8fd9\u4e2a\u3002<\/p>\n\n\n\n
<\/p>\n\n\n\n
4. Explain \u4e3b\u8981\u5173\u6ce8\u70b9<\/h3>\n\n\n\n
\u603b\u7684\u6765\u8bf4\uff0c\u6211\u4eec\u53ea\u9700\u8981\u5173\u6ce8\u7ed3\u679c\u4e2d\u7684\u51e0\u5217\uff1a<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\u518d\u6765\u770b\u4e0bExtra<\/code>\u5217\u4e2d\u9700\u8981\u6ce8\u610f\u51fa\u73b0\u7684\u51e0\u79cd\u60c5\u51b5\uff1a<\/p>\n\n\n\n
\"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"
from \uff1a\u7a0b\u5e8f\u5458\u8001\u9a6c\u5934 https:\/\/blog.csdn.net\/weixin_74412978\/arti … \u7ee7\u7eed\u9605\u8bfb10 \u5206\u949f\u6559\u4f1a\u4f60\u5982\u4f55\u770b\u61c2 MySQL \u6267\u884c\u8ba1\u5212<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-15","post","type-post","status-publish","format-standard","hentry","category-mysql"],"_links":{"self":[{"href":"https:\/\/www.shoubashou.com\/index.php?rest_route=\/wp\/v2\/posts\/15","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.shoubashou.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.shoubashou.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.shoubashou.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.shoubashou.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=15"}],"version-history":[{"count":1,"href":"https:\/\/www.shoubashou.com\/index.php?rest_route=\/wp\/v2\/posts\/15\/revisions"}],"predecessor-version":[{"id":33,"href":"https:\/\/www.shoubashou.com\/index.php?rest_route=\/wp\/v2\/posts\/15\/revisions\/33"}],"wp:attachment":[{"href":"https:\/\/www.shoubashou.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=15"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.shoubashou.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=15"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.shoubashou.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=15"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}