<\/p>\n\n\n\n
# \u7b2c09\u7ae0_\u6027\u80fd\u5206\u6790\u5de5\u5177\u7684\u4f7f\u7528\r\n\r\n# 2. \u67e5\u770b\u7cfb\u7edf\u6027\u80fd\u53c2\u6570\r\n\r\n#\u8fde\u63a5MySQL\u670d\u52a1\u5668\u7684\u6b21\u6570\r\nSHOW STATUS LIKE 'connections';\r\n\r\n#MySQL\u670d\u52a1\u5668\u7684\u4e0a\u7ebf\u65f6\u95f4\r\nSHOW STATUS LIKE 'uptime';\r\n\r\n#\u6162\u67e5\u8be2\u7684\u6b21\u6570\r\nSHOW STATUS LIKE 'slow_queries';\r\n\r\n#Innodb_rows_read SELECT\u67e5\u8be2\u8fd4\u56de\u7684\u884c\u6570\r\n#Innodb_rows_inserted \u6267\u884cINSERT\u64cd\u4f5c\u63d2\u5165\u7684\u884c\u6570\r\n#Innodb_rows_updated \u6267\u884cUPDATE\u64cd\u4f5c\u66f4\u65b0\u7684\u884c\u6570\r\n#Innodb_rows_deleted \u6267\u884cDELETE\u64cd\u4f5c\u5220\u9664\u7684\u884c\u6570\r\nSHOW STATUS LIKE 'innodb_row_%';\r\n\r\nSHOW DATABASES;\r\n\r\nUSE atguigudb;\r\n\r\nSHOW TABLES;\r\n\r\nSELECT * FROM employees;\r\n\r\n#\u67e5\u8be2\u64cd\u4f5c\u7684\u6b21\u6570\r\nSHOW STATUS LIKE 'Com_%select';\r\n#\u63d2\u5165\u64cd\u4f5c\u7684\u6b21\u6570\uff0c\u5bf9\u4e8e\u6279\u91cf\u63d2\u5165\u7684INSERT\u64cd\u4f5c\uff0c\u53ea\u7d2f\u52a0\u4e00\u6b21\r\nSHOW STATUS LIKE 'Com_%insert';\r\n#\u66f4\u65b0\u64cd\u4f5c\u7684\u6b21\u6570\r\nSHOW STATUS LIKE 'Com_%update';\r\n#\u5220\u9664\u64cd\u4f5c\u7684\u6b21\u6570\r\nSHOW STATUS LIKE 'Com_%delete';\r\n\r\n# 3. \u7edf\u8ba1SQL\u7684\u67e5\u8be2\u6210\u672c\uff1alast_query_cost\r\n\r\nUSE atguigudb1;\r\n\r\nSHOW TABLES;\r\n\r\nSELECT * FROM student_info\r\nWHERE id = 900001;\r\n\r\nSHOW STATUS LIKE 'last_query_cost';\r\n\r\nSELECT * FROM student_info\r\nWHERE id BETWEEN 900001 AND 900100;\r\n\r\nSHOW STATUS LIKE 'last_query_cost';\r\n\r\nSELECT * FROM student_info\r\nWHERE student_id > 199000;\r\n\r\nSHOW STATUS LIKE 'last_query_cost';\r\n\r\nSELECT * FROM student_info\r\nWHERE student_id > 199900;\r\n\r\n# 4. \u5b9a\u4f4d\u6267\u884c\u6162\u7684 SQL\uff1a\u6162\u67e5\u8be2\u65e5\u5fd7\r\n\r\n# 4.1 \u5f00\u542f\u6162\u67e5\u8be2\u65e5\u5fd7\u53c2\u6570\r\n\r\n# \u2460 \u5f00\u542fslow_query_log\r\nSHOW VARIABLES LIKE 'slow_query_log';\r\n\r\nSET GLOBAL SLOW_QUERY_LOG = ON;\r\n\r\nSHOW VARIABLES LIKE 'slow_query_log';\r\n\r\nSHOW VARIABLES LIKE 'slow_query_log%';\r\n\r\n# \u2461 \u4fee\u6539long_query_time\u9608\u503c\r\nSHOW VARIABLES LIKE '%long_query_time%';\r\n\r\nSET GLOBAL LONG_QUERY_TIME = 1;\r\n\r\nSHOW GLOBAL VARIABLES LIKE 'long_query_time%';\r\n\r\nSET LONG_QUERY_TIME = 1;\r\n\r\nSHOW VARIABLES LIKE 'long_query_time%';\r\n\r\n# 4.2 \u67e5\u770b\u6162\u67e5\u8be2\u6570\u76ee\r\n\r\nSHOW GLOBAL STATUS LIKE 'Slow_queries%';\r\n\r\n# 4.3 \u6848\u4f8b\u6f14\u793a\r\n\r\nUSE atguigudb1;\r\n\r\n# \u6b65\u9aa41. \u5efa\u8868\r\nCREATE TABLE `student` (\r\n `id` INT(11) NOT NULL AUTO_INCREMENT,\r\n `stuno` INT NOT NULL,\r\n `name` VARCHAR(20) DEFAULT NULL,\r\n `age` INT(3) DEFAULT NULL,\r\n `classId` INT(11) DEFAULT NULL,\r\n PRIMARY KEY (`id`)\r\n) ENGINE=INNODB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;\r\n\r\n# \u6b65\u9aa42\uff1a\u8bbe\u7f6e\u53c2\u6570 log_bin_trust_function_creators\r\nSET GLOBAL log_bin_trust_function_creators=1; # \u4e0d\u52a0global\u53ea\u662f\u5f53\u524d\u7a97\u53e3\u6709\u6548\u3002\r\n\r\n# \u6b65\u9aa43\uff1a\u521b\u5efa\u51fd\u6570\r\n\r\n# \u968f\u673a\u4ea7\u751f\u5b57\u7b26\u4e32\uff1a\r\nDELIMITER \/\/\r\nCREATE FUNCTION rand_string(n INT)\r\n RETURNS VARCHAR(255) #\u8be5\u51fd\u6570\u4f1a\u8fd4\u56de\u4e00\u4e2a\u5b57\u7b26\u4e32\r\nBEGIN\r\n DECLARE chars_str VARCHAR(100) DEFAULT\r\n 'abcdefghijklmnopqrstuvwxyzABCDEFJHIJKLMNOPQRSTUVWXYZ';\r\n DECLARE return_str VARCHAR(255) DEFAULT '';\r\n DECLARE i INT DEFAULT 0;\r\n WHILE i < n DO\r\n SET return_str =CONCAT(return_str,SUBSTRING(chars_str,FLOOR(1+RAND()*52),1));\r\n SET i = i + 1;\r\n END WHILE;\r\n RETURN return_str;\r\nEND \/\/\r\nDELIMITER ;\r\n\r\n#\u6d4b\u8bd5\r\nSELECT rand_string(10);\r\n\r\n# \u4ea7\u751f\u968f\u673a\u6570\u503c\uff1a\r\nDELIMITER \/\/\r\nCREATE FUNCTION rand_num (from_num INT ,to_num INT)\r\n RETURNS INT(11)\r\nBEGIN\r\n DECLARE i INT DEFAULT 0;\r\n SET i = FLOOR(from_num +RAND()*(to_num - from_num+1)) ;\r\n RETURN i;\r\nEND \/\/\r\nDELIMITER ;\r\n\r\n#\u6d4b\u8bd5\uff1a\r\nSELECT rand_num(10,100);\r\n\r\n# \u6b65\u9aa44\uff1a\u521b\u5efa\u5b58\u50a8\u8fc7\u7a0b\r\nDELIMITER \/\/\r\nCREATE PROCEDURE insert_stu1( START INT , max_num INT )\r\nBEGIN\r\n DECLARE i INT DEFAULT 0;\r\n SET autocommit = 0; #\u8bbe\u7f6e\u624b\u52a8\u63d0\u4ea4\u4e8b\u52a1\r\n REPEAT #\u5faa\u73af\r\n SET i = i + 1; #\u8d4b\u503c\r\n INSERT INTO student (stuno, NAME ,age ,classId ) VALUES\r\n ((START+i),rand_string(6),rand_num(10,100),rand_num(10,1000));\r\n UNTIL i = max_num\r\n END REPEAT;\r\n COMMIT; #\u63d0\u4ea4\u4e8b\u52a1\r\nEND \/\/\r\nDELIMITER ;\r\n\r\n# \u6b65\u9aa45\uff1a\u8c03\u7528\u5b58\u50a8\u8fc7\u7a0b\r\nCALL insert_stu1(100001,4000000);\r\n\r\nSELECT COUNT(*) FROM student;\r\n\r\n# 4.4 \u6d4b\u8bd5\u53ca\u5206\u6790\r\n\r\nDESC student;\r\n\r\nSELECT * FROM student\r\nWHERE stuno = 3453451;\r\n\r\nSELECT * FROM student\r\nWHERE name = 'UXeFLN';\r\n\r\nSHOW STATUS LIKE 'slow_queries';\r\n\r\n# 4.5 \u6162\u67e5\u8be2\u65e5\u5fd7\u5206\u6790\u5de5\u5177\uff1amysqldumpslow\r\n\r\n# linux \u4e0b\u6267\u884c\r\n\r\n# mysqldumpslow --help\r\n\r\n# cd \/var\/lib\/mysql\r\n# ll\r\n# \u4e3e\u4f8b\uff1a\u6211\u4eec\u60f3\u8981\u6309\u7167\u67e5\u8be2\u65f6\u95f4\u6392\u5e8f\uff0c\u67e5\u770b\u524d\u4e94\u6761 SQL \u8bed\u53e5\uff0c\u8fd9\u6837\u5199\u5373\u53ef\uff1a\r\n# mysqldumpslow -s t -t 5 \/var\/lib\/mysql\/server2-slow.log\r\n# mysqldumpslow -a -s t -t 5 \/var\/lib\/mysql\/server2-slow.log\r\n\r\n# -a: \u4e0d\u5c06\u6570\u5b57\u62bd\u8c61\u6210N\uff0c\u5b57\u7b26\u4e32\u62bd\u8c61\u6210S\r\n# -s: \u662f\u8868\u793a\u6309\u7167\u4f55\u79cd\u65b9\u5f0f\u6392\u5e8f\uff1a\r\n# c: \u8bbf\u95ee\u6b21\u6570\r\n# l: \u9501\u5b9a\u65f6\u95f4\r\n# r: \u8fd4\u56de\u8bb0\u5f55\r\n# t: \u67e5\u8be2\u65f6\u95f4\r\n# al:\u5e73\u5747\u9501\u5b9a\u65f6\u95f4\r\n# ar:\u5e73\u5747\u8fd4\u56de\u8bb0\u5f55\u6570\r\n# at:\u5e73\u5747\u67e5\u8be2\u65f6\u95f4 \uff08\u9ed8\u8ba4\u65b9\u5f0f\uff09\r\n# ac:\u5e73\u5747\u67e5\u8be2\u6b21\u6570\r\n# -t: \u5373\u4e3a\u8fd4\u56de\u524d\u9762\u591a\u5c11\u6761\u7684\u6570\u636e\uff1b\r\n# -g: \u540e\u8fb9\u642d\u914d\u4e00\u4e2a\u6b63\u5219\u5339\u914d\u6a21\u5f0f\uff0c\u5927\u5c0f\u5199\u4e0d\u654f\u611f\u7684\uff1b\r\n\r\n# \u5de5\u4f5c\u5e38\u7528\u53c2\u8003\uff1a\r\n#\u5f97\u5230\u8fd4\u56de\u8bb0\u5f55\u96c6\u6700\u591a\u768410\u4e2aSQL\r\n# mysqldumpslow -s r -t 10 \/var\/lib\/mysql\/server2-slow.log\r\n#\u5f97\u5230\u8bbf\u95ee\u6b21\u6570\u6700\u591a\u768410\u4e2aSQL\r\n# mysqldumpslow -s c -t 10 \/var\/lib\/mysql\/server2-slow.log\r\n#\u5f97\u5230\u6309\u7167\u65f6\u95f4\u6392\u5e8f\u7684\u524d10\u6761\u91cc\u9762\u542b\u6709\u5de6\u8fde\u63a5\u7684\u67e5\u8be2\u8bed\u53e5\r\n# mysqldumpslow -s t -t 10 -g \"left join\" \/var\/lib\/mysql\/server2-slow.log\r\n#\u53e6\u5916\u5efa\u8bae\u5728\u4f7f\u7528\u8fd9\u4e9b\u547d\u4ee4\u65f6\u7ed3\u5408 | \u548cmore \u4f7f\u7528 \uff0c\u5426\u5219\u6709\u53ef\u80fd\u51fa\u73b0\u7206\u5c4f\u60c5\u51b5\r\n# mysqldumpslow -s r -t 10 \/var\/lib\/mysql\/server2-slow.log | more\r\n\r\n# 4.6 \u5173\u95ed\u6162\u67e5\u8be2\u65e5\u5fd7\r\n\r\nSET GLOBAL SLOW_QUERY_LOG=OFF;\r\n\r\nSHOW VARIABLES LIKE '%slow%';\r\n\r\nSHOW VARIABLES LIKE '%long_query_time%';\r\n\r\n# 4.7 \u5220\u9664\u6162\u67e5\u8be2\u65e5\u5fd7\r\n\r\n# linux \u4e0b\u6267\u884c\r\n\r\n# rm server2-slow.log\r\n\r\n# mysqladmin -uroot -p flush-logs slow\r\n\r\n# 5. \u67e5\u770b SQL \u6267\u884c\u6210\u672c\uff1aSHOW PROFILE\r\n\r\nSHOW VARIABLES LIKE 'profiling';\r\n\r\nSET PROFILING = 'ON';\r\n\r\nSHOW VARIABLES LIKE 'profiling';\r\n\r\nSELECT * FROM student\r\nWHERE name = 'UXeFLN';\r\n\r\nSHOW PROFILES;\r\n\r\nSHOW PROFILE;\r\n\r\nSHOW PROFILE CPU,BLOCK IO FOR QUERY 3;\r\n\r\n# 6. \u5206\u6790\u67e5\u8be2\u8bed\u53e5\uff1aEXPLAIN\r\n\r\n# 6.1 \u6982\u8ff0\r\n\r\n#\u4ec0\u4e48\u662f\u6267\u884c\u8ba1\u5212\uff1f\r\nEXPLAIN SELECT * FROM student_info;\r\n\r\nSELECT * FROM student_info\r\nLIMIT 10;\r\n\r\nDESCRIBE DELETE FROM student_info\r\nWHERE id = 2;\r\n\r\n# \u7248\u672c\u60c5\u51b5\r\n\r\n# \u57285.7\u4ee5\u524d\u7684\u7248\u672c\u4e2d\uff0c\r\n# \u60f3\u8981\u663e\u793a partitions \u9700\u8981\u4f7f\u7528 explain partitions \u547d\u4ee4\uff1b\r\n# \u60f3\u8981\u663e\u793afiltered \u9700\u8981\u4f7f\u7528 explain extended \u547d\u4ee4\u3002\r\n# \u57285.7\u7248\u672c\u540e\uff0c\u9ed8\u8ba4explain\u76f4\u63a5\u663e\u793apartitions\u548cfiltered\u4e2d\u7684\u4fe1\u606f\u3002\r\n\r\n# 6.2 \u57fa\u672c\u8bed\u6cd5\r\n\r\n# EXPLAIN \u8bed\u53e5\u8f93\u51fa\u7684\u5404\u4e2a\u5217\u7684\u4f5c\u7528\u5982\u4e0b\uff1a\r\n\r\n# \u5217\u540d \u91cd\u8981 \u63cf\u8ff0\r\n# id \u5728\u4e00\u4e2a\u5927\u7684\u67e5\u8be2\u8bed\u53e5\u4e2d\u6bcf\u4e2aSELECT\u5173\u952e\u5b57\u90fd\u5bf9\u5e94\u4e00\u4e2a \u552f\u4e00\u7684id\r\n# select_type SELECT\u5173\u952e\u5b57\u5bf9\u5e94\u7684\u90a3\u4e2a\u67e5\u8be2\u7684\u7c7b\u578b\r\n# table \u8868\u540d\r\n# partitions \u5339\u914d\u7684\u5206\u533a\u4fe1\u606f\r\n# type \u2606 \u9488\u5bf9\u5355\u8868\u7684\u8bbf\u95ee\u65b9\u6cd5\r\n# possible_keys \u53ef\u80fd\u7528\u5230\u7684\u7d22\u5f15\r\n# key \u5b9e\u9645\u4e0a\u4f7f\u7528\u7684\u7d22\u5f15\r\n# key_len \u2606 \u5b9e\u9645\u4f7f\u7528\u5230\u7684\u7d22\u5f15\u957f\u5ea6\r\n# ref \u5f53\u4f7f\u7528\u7d22\u5f15\u5217\u7b49\u503c\u67e5\u8be2\u65f6\uff0c\u4e0e\u7d22\u5f15\u5217\u8fdb\u884c\u7b49\u503c\u5339\u914d\u7684\u5bf9\u8c61\u4fe1\u606f\r\n# rows \u2606 \u9884\u4f30\u7684\u9700\u8981\u8bfb\u53d6\u7684\u8bb0\u5f55\u6761\u6570\r\n# filtered \u67d0\u4e2a\u8868\u7ecf\u8fc7\u641c\u7d22\u6761\u4ef6\u8fc7\u6ee4\u540e\u5269\u4f59\u8bb0\u5f55\u6761\u6570\u7684\u767e\u5206\u6bd4\r\n# Extra \u2606 \u4e00\u4e9b\u989d\u5916\u7684\u4fe1\u606f\r\n\r\n# 6.3 \u6570\u636e\u51c6\u5907\r\n\r\n#\r\nUSE atguigudb1;\r\n\r\n# 1. \u521b\u5efa\u8868\r\nCREATE TABLE s1 (\r\n id INT AUTO_INCREMENT,\r\n key1 VARCHAR(100),\r\n key2 INT,\r\n key3 VARCHAR(100),\r\n key_part1 VARCHAR(100),\r\n key_part2 VARCHAR(100),\r\n key_part3 VARCHAR(100),\r\n common_field VARCHAR(100),\r\n PRIMARY KEY (id),\r\n INDEX idx_key1 (key1),\r\n UNIQUE INDEX idx_key2 (key2),\r\n INDEX idx_key3 (key3),\r\n INDEX idx_key_part(key_part1, key_part2, key_part3)\r\n) ENGINE=INNODB CHARSET=utf8;\r\n\r\nCREATE TABLE s2 (\r\n id INT AUTO_INCREMENT,\r\n key1 VARCHAR(100),\r\n key2 INT,\r\n key3 VARCHAR(100),\r\n key_part1 VARCHAR(100),\r\n key_part2 VARCHAR(100),\r\n key_part3 VARCHAR(100),\r\n common_field VARCHAR(100),\r\n PRIMARY KEY (id),\r\n INDEX idx_key1 (key1),\r\n UNIQUE INDEX idx_key2 (key2),\r\n INDEX idx_key3 (key3),\r\n INDEX idx_key_part(key_part1, key_part2, key_part3)\r\n) ENGINE=INNODB CHARSET=utf8;\r\n\r\n# 2. \u8bbe\u7f6e\u53c2\u6570 log_bin_trust_function_creators\r\nSET GLOBAL log_bin_trust_function_creators=1; # \u4e0d\u52a0global\u53ea\u662f\u5f53\u524d\u7a97\u53e3\u6709\u6548\u3002\r\n\r\n# 3. \u521b\u5efa\u51fd\u6570\r\nDELIMITER \/\/\r\nCREATE FUNCTION rand_string1(n INT)\r\n RETURNS VARCHAR(255) #\u8be5\u51fd\u6570\u4f1a\u8fd4\u56de\u4e00\u4e2a\u5b57\u7b26\u4e32\r\nBEGIN\r\n DECLARE chars_str VARCHAR(100) DEFAULT\r\n 'abcdefghijklmnopqrstuvwxyzABCDEFJHIJKLMNOPQRSTUVWXYZ';\r\n DECLARE return_str VARCHAR(255) DEFAULT '';\r\n DECLARE i INT DEFAULT 0;\r\n WHILE i < n DO\r\n SET return_str =CONCAT(return_str,SUBSTRING(chars_str,FLOOR(1+RAND()*52),1));\r\n SET i = i + 1;\r\n END WHILE;\r\n RETURN return_str;\r\nEND \/\/\r\nDELIMITER ;\r\n\r\n# 4. \u521b\u5efa\u5b58\u50a8\u8fc7\u7a0b\r\n\r\n# \u521b\u5efa\u5f80s1\u8868\u4e2d\u63d2\u5165\u6570\u636e\u7684\u5b58\u50a8\u8fc7\u7a0b\uff1a\r\nDELIMITER \/\/\r\nCREATE PROCEDURE insert_s1 (IN min_num INT (10),IN max_num INT (10))\r\nBEGIN\r\n DECLARE i INT DEFAULT 0;\r\n SET autocommit = 0;\r\n REPEAT\r\n SET i = i + 1;\r\n INSERT INTO s1 VALUES(\r\n (min_num + i),\r\n rand_string1(6),\r\n (min_num + 30 * i + 5),\r\n rand_string1(6),\r\n rand_string1(10),\r\n rand_string1(5),\r\n rand_string1(10),\r\n rand_string1(10));\r\n UNTIL i = max_num\r\n END REPEAT;\r\n COMMIT;\r\nEND \/\/\r\nDELIMITER ;\r\n\r\n# \u521b\u5efa\u5f80s2\u8868\u4e2d\u63d2\u5165\u6570\u636e\u7684\u5b58\u50a8\u8fc7\u7a0b\uff1a\r\nDELIMITER \/\/\r\nCREATE PROCEDURE insert_s2 (IN min_num INT (10),IN max_num INT (10))\r\nBEGIN\r\n DECLARE i INT DEFAULT 0;\r\n SET autocommit = 0;\r\n REPEAT\r\n SET i = i + 1;\r\n INSERT INTO s2 VALUES(\r\n (min_num + i),\r\n rand_string1(6),\r\n (min_num + 30 * i + 5),\r\n rand_string1(6),\r\n rand_string1(10),\r\n rand_string1(5),\r\n rand_string1(10),\r\n rand_string1(10));\r\n UNTIL i = max_num\r\n END REPEAT;\r\n COMMIT;\r\nEND \/\/\r\nDELIMITER ;\r\n\r\n# 5. \u8c03\u7528\u5b58\u50a8\u8fc7\u7a0b\r\nCALL insert_s1(10001,10000);\r\n\r\nCALL insert_s2(10001,10000);\r\n\r\nSELECT COUNT(*) FROM s1;\r\n\r\nSELECT COUNT(*) FROM s2;\r\n\r\n# 6.4 EXPLAIN\u5404\u5217\u4f5c\u7528\r\n\r\n #1. table\uff1a\u8868\u540d\r\n #\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u8bb0\u5f55\u90fd\u5bf9\u5e94\u7740\u4e00\u4e2a\u5355\u8868\r\n EXPLAIN SELECT * FROM s1;\r\n\r\n #s1:\u9a71\u52a8\u8868 s2:\u88ab\u9a71\u52a8\u8868\r\n EXPLAIN SELECT * FROM s1 INNER JOIN s2;\r\n\r\n #2. id\uff1a\u5728\u4e00\u4e2a\u5927\u7684\u67e5\u8be2\u8bed\u53e5\u4e2d\u6bcf\u4e2aSELECT\u5173\u952e\u5b57\u90fd\u5bf9\u5e94\u4e00\u4e2a\u552f\u4e00\u7684id\r\n EXPLAIN SELECT * FROM s1 WHERE key1 = 'a';\r\n\r\n EXPLAIN SELECT * FROM s1 INNER JOIN s2\r\n ON s1.key1 = s2.key1\r\n WHERE s1.common_field = 'a';\r\n\r\n EXPLAIN SELECT * FROM s1\r\n WHERE key1 IN (SELECT key3 FROM s2);\r\n\r\n EXPLAIN SELECT * FROM s1 UNION SELECT * FROM s2;\r\n\r\n EXPLAIN SELECT * FROM s1 WHERE key1 = 'a';\r\n\r\n EXPLAIN SELECT * FROM s1 INNER JOIN s2;\r\n\r\n EXPLAIN SELECT * FROM s1 WHERE key1 IN (SELECT key1 FROM s2) OR key3 = 'a';\r\n\r\n ######\u67e5\u8be2\u4f18\u5316\u5668\u53ef\u80fd\u5bf9\u6d89\u53ca\u5b50\u67e5\u8be2\u7684\u67e5\u8be2\u8bed\u53e5\u8fdb\u884c\u91cd\u5199,\u8f6c\u53d8\u4e3a\u591a\u8868\u67e5\u8be2\u7684\u64cd\u4f5c########\r\n EXPLAIN SELECT * FROM s1 WHERE key1 IN (SELECT key2 FROM s2 WHERE common_field = 'a');\r\n\r\n #Union\u53bb\u91cd\r\n EXPLAIN SELECT * FROM s1 UNION SELECT * FROM s2;\r\n\r\n EXPLAIN SELECT * FROM s1 UNION ALL SELECT * FROM s2;\r\n\r\n #3. select_type\uff1aSELECT\u5173\u952e\u5b57\u5bf9\u5e94\u7684\u90a3\u4e2a\u67e5\u8be2\u7684\u7c7b\u578b,\u786e\u5b9a\u5c0f\u67e5\u8be2\u5728\u6574\u4e2a\u5927\u67e5\u8be2\u4e2d\u626e\u6f14\u4e86\u4e00\u4e2a\u4ec0\u4e48\u89d2\u8272\r\n\r\n # \u67e5\u8be2\u8bed\u53e5\u4e2d\u4e0d\u5305\u542b`UNION`\u6216\u8005\u5b50\u67e5\u8be2\u7684\u67e5\u8be2\u90fd\u7b97\u4f5c\u662f`SIMPLE`\u7c7b\u578b\r\n EXPLAIN SELECT * FROM s1;\r\n\r\n #\u8fde\u63a5\u67e5\u8be2\u4e5f\u7b97\u662f`SIMPLE`\u7c7b\u578b\r\n EXPLAIN SELECT * FROM s1 INNER JOIN s2;\r\n\r\n #\u5bf9\u4e8e\u5305\u542b`UNION`\u6216\u8005`UNION ALL`\u6216\u8005\u5b50\u67e5\u8be2\u7684\u5927\u67e5\u8be2\u6765\u8bf4\uff0c\u5b83\u662f\u7531\u51e0\u4e2a\u5c0f\u67e5\u8be2\u7ec4\u6210\u7684\uff0c\u5176\u4e2d\u6700\u5de6\u8fb9\u7684\u90a3\u4e2a\r\n #\u67e5\u8be2\u7684`select_type`\u503c\u5c31\u662f`PRIMARY`\r\n\r\n #\u5bf9\u4e8e\u5305\u542b`UNION`\u6216\u8005`UNION ALL`\u7684\u5927\u67e5\u8be2\u6765\u8bf4\uff0c\u5b83\u662f\u7531\u51e0\u4e2a\u5c0f\u67e5\u8be2\u7ec4\u6210\u7684\uff0c\u5176\u4e2d\u9664\u4e86\u6700\u5de6\u8fb9\u7684\u90a3\u4e2a\u5c0f\u67e5\u8be2\r\n #\u4ee5\u5916\uff0c\u5176\u4f59\u7684\u5c0f\u67e5\u8be2\u7684`select_type`\u503c\u5c31\u662f`UNION`\r\n\r\n #`MySQL`\u9009\u62e9\u4f7f\u7528\u4e34\u65f6\u8868\u6765\u5b8c\u6210`UNION`\u67e5\u8be2\u7684\u53bb\u91cd\u5de5\u4f5c\uff0c\u9488\u5bf9\u8be5\u4e34\u65f6\u8868\u7684\u67e5\u8be2\u7684`select_type`\u5c31\u662f\r\n #`UNION RESULT`\r\n EXPLAIN SELECT * FROM s1 UNION SELECT * FROM s2;\r\n\r\n EXPLAIN SELECT * FROM s1 UNION ALL SELECT * FROM s2;\r\n\r\n #\u5b50\u67e5\u8be2\uff1a\r\n #\u5982\u679c\u5305\u542b\u5b50\u67e5\u8be2\u7684\u67e5\u8be2\u8bed\u53e5\u4e0d\u80fd\u591f\u8f6c\u4e3a\u5bf9\u5e94\u7684`semi-join`\u7684\u5f62\u5f0f\uff0c\u5e76\u4e14\u8be5\u5b50\u67e5\u8be2\u662f\u4e0d\u76f8\u5173\u5b50\u67e5\u8be2\u3002\r\n #\u8be5\u5b50\u67e5\u8be2\u7684\u7b2c\u4e00\u4e2a`SELECT`\u5173\u952e\u5b57\u4ee3\u8868\u7684\u90a3\u4e2a\u67e5\u8be2\u7684`select_type`\u5c31\u662f`SUBQUERY`\r\n EXPLAIN SELECT * FROM s1 WHERE key1 IN (SELECT key1 FROM s2) OR key3 = 'a';\r\n\r\n #\u5982\u679c\u5305\u542b\u5b50\u67e5\u8be2\u7684\u67e5\u8be2\u8bed\u53e5\u4e0d\u80fd\u591f\u8f6c\u4e3a\u5bf9\u5e94\u7684`semi-join`\u7684\u5f62\u5f0f\uff0c\u5e76\u4e14\u8be5\u5b50\u67e5\u8be2\u662f\u76f8\u5173\u5b50\u67e5\u8be2\uff0c\r\n #\u5219\u8be5\u5b50\u67e5\u8be2\u7684\u7b2c\u4e00\u4e2a`SELECT`\u5173\u952e\u5b57\u4ee3\u8868\u7684\u90a3\u4e2a\u67e5\u8be2\u7684`select_type`\u5c31\u662f`DEPENDENT SUBQUERY`\r\n EXPLAIN SELECT * FROM s1\r\n WHERE key1 IN (SELECT key1 FROM s2 WHERE s1.key2 = s2.key2) OR key3 = 'a';\r\n #\u6ce8\u610f\u7684\u662f\uff0cselect_type\u4e3a`DEPENDENT SUBQUERY`\u7684\u67e5\u8be2\u53ef\u80fd\u4f1a\u88ab\u6267\u884c\u591a\u6b21\u3002\r\n\r\n #\u5728\u5305\u542b`UNION`\u6216\u8005`UNION ALL`\u7684\u5927\u67e5\u8be2\u4e2d\uff0c\u5982\u679c\u5404\u4e2a\u5c0f\u67e5\u8be2\u90fd\u4f9d\u8d56\u4e8e\u5916\u5c42\u67e5\u8be2\u7684\u8bdd\uff0c\u90a3\u9664\u4e86\r\n #\u6700\u5de6\u8fb9\u7684\u90a3\u4e2a\u5c0f\u67e5\u8be2\u4e4b\u5916\uff0c\u5176\u4f59\u7684\u5c0f\u67e5\u8be2\u7684`select_type`\u7684\u503c\u5c31\u662f`DEPENDENT UNION`\u3002\r\n EXPLAIN SELECT * FROM s1\r\n WHERE key1 IN (SELECT key1 FROM s2 WHERE key1 = 'a' UNION SELECT key1 FROM s1 WHERE key1 = 'b');\r\n\r\n #\u5bf9\u4e8e\u5305\u542b`\u6d3e\u751f\u8868`\u7684\u67e5\u8be2\uff0c\u8be5\u6d3e\u751f\u8868\u5bf9\u5e94\u7684\u5b50\u67e5\u8be2\u7684`select_type`\u5c31\u662f`DERIVED`\r\n EXPLAIN SELECT *\r\n FROM (SELECT key1, COUNT(*) AS c FROM s1 GROUP BY key1) AS derived_s1 WHERE c > 1;\r\n\r\n #\u5f53\u67e5\u8be2\u4f18\u5316\u5668\u5728\u6267\u884c\u5305\u542b\u5b50\u67e5\u8be2\u7684\u8bed\u53e5\u65f6\uff0c\u9009\u62e9\u5c06\u5b50\u67e5\u8be2\u7269\u5316\u4e4b\u540e\u4e0e\u5916\u5c42\u67e5\u8be2\u8fdb\u884c\u8fde\u63a5\u67e5\u8be2\u65f6\uff0c\r\n #\u8be5\u5b50\u67e5\u8be2\u5bf9\u5e94\u7684`select_type`\u5c5e\u6027\u5c31\u662f`MATERIALIZED`\r\n EXPLAIN SELECT * FROM s1 WHERE key1 IN (SELECT key1 FROM s2); #\u5b50\u67e5\u8be2\u88ab\u8f6c\u4e3a\u4e86\u7269\u5316\u8868\r\n\r\n # 4. partition(\u7565)\uff1a\u5339\u914d\u7684\u5206\u533a\u4fe1\u606f\r\n\r\n # 5. type\uff1a\u9488\u5bf9\u5355\u8868\u7684\u8bbf\u95ee\u65b9\u6cd5\r\n\r\n #\u5f53\u8868\u4e2d`\u53ea\u6709\u4e00\u6761\u8bb0\u5f55`\u5e76\u4e14\u8be5\u8868\u4f7f\u7528\u7684\u5b58\u50a8\u5f15\u64ce\u7684\u7edf\u8ba1\u6570\u636e\u662f\u7cbe\u786e\u7684\uff0c\u6bd4\u5982MyISAM\u3001Memory\uff0c\r\n #\u90a3\u4e48\u5bf9\u8be5\u8868\u7684\u8bbf\u95ee\u65b9\u6cd5\u5c31\u662f`system`\u3002\r\n CREATE TABLE t(i INT) ENGINE=MYISAM;\r\n INSERT INTO t VALUES(1);\r\n\r\n EXPLAIN SELECT * FROM t;\r\n\r\n #\u6362\u6210InnoDB\r\n CREATE TABLE tt(i INT) ENGINE=INNODB;\r\n INSERT INTO tt VALUES(1);\r\n EXPLAIN SELECT * FROM tt;\r\n\r\n #\u5f53\u6211\u4eec\u6839\u636e\u4e3b\u952e\u6216\u8005\u552f\u4e00\u4e8c\u7ea7\u7d22\u5f15\u5217\u4e0e\u5e38\u6570\u8fdb\u884c\u7b49\u503c\u5339\u914d\u65f6\uff0c\u5bf9\u5355\u8868\u7684\u8bbf\u95ee\u65b9\u6cd5\u5c31\u662f`const`\r\n EXPLAIN SELECT * FROM s1 WHERE id = 10005;\r\n\r\n EXPLAIN SELECT * FROM s1 WHERE key2 = 10066;\r\n\r\n #\u5728\u8fde\u63a5\u67e5\u8be2\u65f6\uff0c\u5982\u679c\u88ab\u9a71\u52a8\u8868\u662f\u901a\u8fc7\u4e3b\u952e\u6216\u8005\u552f\u4e00\u4e8c\u7ea7\u7d22\u5f15\u5217\u7b49\u503c\u5339\u914d\u7684\u65b9\u5f0f\u8fdb\u884c\u8bbf\u95ee\u7684\r\n #\uff08\u5982\u679c\u8be5\u4e3b\u952e\u6216\u8005\u552f\u4e00\u4e8c\u7ea7\u7d22\u5f15\u662f\u8054\u5408\u7d22\u5f15\u7684\u8bdd\uff0c\u6240\u6709\u7684\u7d22\u5f15\u5217\u90fd\u5fc5\u987b\u8fdb\u884c\u7b49\u503c\u6bd4\u8f83\uff09\uff0c\u5219\r\n #\u5bf9\u8be5\u88ab\u9a71\u52a8\u8868\u7684\u8bbf\u95ee\u65b9\u6cd5\u5c31\u662f`eq_ref`\r\n EXPLAIN SELECT * FROM s1 INNER JOIN s2 ON s1.id = s2.id;\r\n\r\n #\u5f53\u901a\u8fc7\u666e\u901a\u7684\u4e8c\u7ea7\u7d22\u5f15\u5217\u4e0e\u5e38\u91cf\u8fdb\u884c\u7b49\u503c\u5339\u914d\u65f6\u6765\u67e5\u8be2\u67d0\u4e2a\u8868\uff0c\u90a3\u4e48\u5bf9\u8be5\u8868\u7684\u8bbf\u95ee\u65b9\u6cd5\u5c31\u53ef\u80fd\u662f`ref`\r\n EXPLAIN SELECT * FROM s1 WHERE key1 = 'a';\r\n\r\n #\u5f53\u5bf9\u666e\u901a\u4e8c\u7ea7\u7d22\u5f15\u8fdb\u884c\u7b49\u503c\u5339\u914d\u67e5\u8be2\uff0c\u8be5\u7d22\u5f15\u5217\u7684\u503c\u4e5f\u53ef\u4ee5\u662f`NULL`\u503c\u65f6\uff0c\u90a3\u4e48\u5bf9\u8be5\u8868\u7684\u8bbf\u95ee\u65b9\u6cd5\r\n #\u5c31\u53ef\u80fd\u662f`ref_or_null`\r\n EXPLAIN SELECT * FROM s1 WHERE key1 = 'a' OR key1 IS NULL;\r\n\r\n #\u5355\u8868\u8bbf\u95ee\u65b9\u6cd5\u65f6\u5728\u67d0\u4e9b\u573a\u666f\u4e0b\u53ef\u4ee5\u4f7f\u7528`Intersection`\u3001`Union`\u3001\r\n #`Sort-Union`\u8fd9\u4e09\u79cd\u7d22\u5f15\u5408\u5e76\u7684\u65b9\u5f0f\u6765\u6267\u884c\u67e5\u8be2\r\n EXPLAIN SELECT * FROM s1 WHERE key1 = 'a' OR key3 = 'a';\r\n\r\n #`unique_subquery`\u662f\u9488\u5bf9\u5728\u4e00\u4e9b\u5305\u542b`IN`\u5b50\u67e5\u8be2\u7684\u67e5\u8be2\u8bed\u53e5\u4e2d\uff0c\u5982\u679c\u67e5\u8be2\u4f18\u5316\u5668\u51b3\u5b9a\u5c06`IN`\u5b50\u67e5\u8be2\r\n #\u8f6c\u6362\u4e3a`EXISTS`\u5b50\u67e5\u8be2\uff0c\u800c\u4e14\u5b50\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528\u5230\u4e3b\u952e\u8fdb\u884c\u7b49\u503c\u5339\u914d\u7684\u8bdd\uff0c\u90a3\u4e48\u8be5\u5b50\u67e5\u8be2\u6267\u884c\u8ba1\u5212\u7684`type`\r\n #\u5217\u7684\u503c\u5c31\u662f`unique_subquery`\r\n EXPLAIN SELECT * FROM s1\r\n WHERE key2 IN (SELECT id FROM s2 WHERE s1.key1 = s2.key1) OR key3 = 'a';\r\n\r\n #\u5982\u679c\u4f7f\u7528\u7d22\u5f15\u83b7\u53d6\u67d0\u4e9b`\u8303\u56f4\u533a\u95f4`\u7684\u8bb0\u5f55\uff0c\u90a3\u4e48\u5c31\u53ef\u80fd\u4f7f\u7528\u5230`range`\u8bbf\u95ee\u65b9\u6cd5\r\n EXPLAIN SELECT * FROM s1 WHERE key1 IN ('a', 'b', 'c');\r\n\r\n #\u540c\u4e0a\r\n EXPLAIN SELECT * FROM s1 WHERE key1 > 'a' AND key1 < 'b';\r\n\r\n #\u5f53\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u7d22\u5f15\u8986\u76d6\uff0c\u4f46\u9700\u8981\u626b\u63cf\u5168\u90e8\u7684\u7d22\u5f15\u8bb0\u5f55\u65f6\uff0c\u8be5\u8868\u7684\u8bbf\u95ee\u65b9\u6cd5\u5c31\u662f`index`\r\n EXPLAIN SELECT key_part2 FROM s1 WHERE key_part3 = 'a';\r\n\r\n #\u6700\u719f\u6089\u7684\u5168\u8868\u626b\u63cf\r\n EXPLAIN SELECT * FROM s1;\r\n\r\n # \u5c0f\u7ed3\uff1a\r\n # \u7ed3\u679c\u503c\u4ece\u6700\u597d\u5230\u6700\u574f\u4f9d\u6b21\u662f\uff1a\r\n # system > const >\r\n # eq_ref > ref >\r\n # fulltext > ref_or_null > index_merge >unique_subquery > index_subquery > range >\r\n # index > ALL\r\n # \u5176\u4e2d\u6bd4\u8f83\u91cd\u8981\u7684\u51e0\u4e2a\u63d0\u53d6\u51fa\u6765\uff08\u89c1\u4e0a\u56fe\u4e2d\u7684\u84dd\u8272\uff09\u3002\r\n # SQL \u6027\u80fd\u4f18\u5316\u7684\u76ee\u6807\uff1a\r\n # \u81f3\u5c11\u8981\u8fbe\u5230 range \u7ea7\u522b\uff0c\u8981\u6c42\u662f ref \u7ea7\u522b\uff0c\u6700\u597d\u662f consts\u7ea7\u522b\u3002\uff08\u963f\u91cc\u5df4\u5df4\u5f00\u53d1\u624b\u518c\u8981\u6c42\uff09\r\n\r\n #6. possible_keys\u548ckey\uff1a\u53ef\u80fd\u7528\u5230\u7684\u7d22\u5f15 \u548c \u5b9e\u9645\u4e0a\u4f7f\u7528\u7684\u7d22\u5f15\r\n\r\n EXPLAIN SELECT * FROM s1 WHERE key1 > 'z' AND key3 = 'a';\r\n\r\n #7. key_len\uff1a\u5b9e\u9645\u4f7f\u7528\u5230\u7684\u7d22\u5f15\u957f\u5ea6(\u5373\uff1a\u5b57\u8282\u6570)\r\n # \u5e2e\u4f60\u68c0\u67e5`\u662f\u5426\u5145\u5206\u7684\u5229\u7528\u4e0a\u4e86\u7d22\u5f15`\uff0c`\u503c\u8d8a\u5927\u8d8a\u597d`,\u4e3b\u8981\u9488\u5bf9\u4e8e\u8054\u5408\u7d22\u5f15\uff0c\u6709\u4e00\u5b9a\u7684\u53c2\u8003\u610f\u4e49\u3002\r\n EXPLAIN SELECT * FROM s1 WHERE id = 10005;\r\n\r\n EXPLAIN SELECT * FROM s1 WHERE key2 = 10126;\r\n\r\n EXPLAIN SELECT * FROM s1 WHERE key1 = 'a';\r\n\r\n EXPLAIN SELECT * FROM s1 WHERE key_part1 = 'a';\r\n\r\n EXPLAIN SELECT * FROM s1 WHERE key_part1 = 'a' AND key_part2 = 'b';\r\n\r\n EXPLAIN SELECT * FROM s1 WHERE key_part1 = 'a' AND key_part2 = 'b' AND key_part3 = 'c';\r\n\r\n EXPLAIN SELECT * FROM s1 WHERE key_part3 = 'a';\r\n\r\n #\u7ec3\u4e60\uff1a\r\n #varchar(10)\u53d8\u957f\u5b57\u6bb5\u4e14\u5141\u8bb8NULL = 10 * ( character set\uff1autf8=3,gbk=2,latin1=1)+1(NULL)+2(\u53d8\u957f\u5b57\u6bb5)\r\n\r\n #varchar(10)\u53d8\u957f\u5b57\u6bb5\u4e14\u4e0d\u5141\u8bb8NULL = 10 * ( character set\uff1autf8=3,gbk=2,latin1=1)+2(\u53d8\u957f\u5b57\u6bb5)\r\n\r\n #char(10)\u56fa\u5b9a\u5b57\u6bb5\u4e14\u5141\u8bb8NULL = 10 * ( character set\uff1autf8=3,gbk=2,latin1=1)+1(NULL)\r\n\r\n #char(10)\u56fa\u5b9a\u5b57\u6bb5\u4e14\u4e0d\u5141\u8bb8NULL = 10 * ( character set\uff1autf8=3,gbk=2,latin1=1)\r\n\r\n # 8. ref\uff1a\u5f53\u4f7f\u7528\u7d22\u5f15\u5217\u7b49\u503c\u67e5\u8be2\u65f6\uff0c\u4e0e\u7d22\u5f15\u5217\u8fdb\u884c\u7b49\u503c\u5339\u914d\u7684\u5bf9\u8c61\u4fe1\u606f\u3002\r\n #\u6bd4\u5982\u53ea\u662f\u4e00\u4e2a\u5e38\u6570\u6216\u8005\u662f\u67d0\u4e2a\u5217\u3002\r\n\r\n EXPLAIN SELECT * FROM s1 WHERE key1 = 'a';\r\n\r\n EXPLAIN SELECT * FROM s1 INNER JOIN s2 ON s1.id = s2.id;\r\n\r\n EXPLAIN SELECT * FROM s1 INNER JOIN s2 ON s2.key1 = UPPER(s1.key1);\r\n\r\n # 9. rows\uff1a\u9884\u4f30\u7684\u9700\u8981\u8bfb\u53d6\u7684\u8bb0\u5f55\u6761\u6570\r\n # `\u503c\u8d8a\u5c0f\u8d8a\u597d`\r\n EXPLAIN SELECT * FROM s1 WHERE key1 > 'z';\r\n\r\n # 10. filtered: \u67d0\u4e2a\u8868\u7ecf\u8fc7\u641c\u7d22\u6761\u4ef6\u8fc7\u6ee4\u540e\u5269\u4f59\u8bb0\u5f55\u6761\u6570\u7684\u767e\u5206\u6bd4\r\n\r\n #\u5982\u679c\u4f7f\u7528\u7684\u662f\u7d22\u5f15\u6267\u884c\u7684\u5355\u8868\u626b\u63cf\uff0c\u90a3\u4e48\u8ba1\u7b97\u65f6\u9700\u8981\u4f30\u8ba1\u51fa\u6ee1\u8db3\u9664\u4f7f\u7528\r\n #\u5230\u5bf9\u5e94\u7d22\u5f15\u7684\u641c\u7d22\u6761\u4ef6\u5916\u7684\u5176\u4ed6\u641c\u7d22\u6761\u4ef6\u7684\u8bb0\u5f55\u6709\u591a\u5c11\u6761\u3002\r\n EXPLAIN SELECT * FROM s1 WHERE key1 > 'z' AND common_field = 'a';\r\n\r\n #\u5bf9\u4e8e\u5355\u8868\u67e5\u8be2\u6765\u8bf4\uff0c\u8fd9\u4e2afiltered\u5217\u7684\u503c\u6ca1\u4ec0\u4e48\u610f\u4e49\uff0c\u6211\u4eec`\u66f4\u5173\u6ce8\u5728\u8fde\u63a5\u67e5\u8be2\r\n #\u4e2d\u9a71\u52a8\u8868\u5bf9\u5e94\u7684\u6267\u884c\u8ba1\u5212\u8bb0\u5f55\u7684filtered\u503c`\uff0c\u5b83\u51b3\u5b9a\u4e86\u88ab\u9a71\u52a8\u8868\u8981\u6267\u884c\u7684\u6b21\u6570(\u5373\uff1arows * filtered)\r\n EXPLAIN SELECT * FROM s1 INNER JOIN s2 ON s1.key1 = s2.key1 WHERE s1.common_field = 'a';\r\n\r\n #11. Extra:\u4e00\u4e9b\u989d\u5916\u7684\u4fe1\u606f\r\n #\u66f4\u51c6\u786e\u7684\u7406\u89e3MySQL\u5230\u5e95\u5c06\u5982\u4f55\u6267\u884c\u7ed9\u5b9a\u7684\u67e5\u8be2\u8bed\u53e5\r\n\r\n #\u5f53\u67e5\u8be2\u8bed\u53e5\u7684\u6ca1\u6709`FROM`\u5b50\u53e5\u65f6\u5c06\u4f1a\u63d0\u793a\u8be5\u989d\u5916\u4fe1\u606f\r\n EXPLAIN SELECT 1;\r\n\r\n #\u67e5\u8be2\u8bed\u53e5\u7684`WHERE`\u5b50\u53e5\u6c38\u8fdc\u4e3a`FALSE`\u65f6\u5c06\u4f1a\u63d0\u793a\u8be5\u989d\u5916\u4fe1\u606f\r\n EXPLAIN SELECT * FROM s1 WHERE 1 != 1;\r\n\r\n #\u5f53\u6211\u4eec\u4f7f\u7528\u5168\u8868\u626b\u63cf\u6765\u6267\u884c\u5bf9\u67d0\u4e2a\u8868\u7684\u67e5\u8be2\uff0c\u5e76\u4e14\u8be5\u8bed\u53e5\u7684`WHERE`\r\n #\u5b50\u53e5\u4e2d\u6709\u9488\u5bf9\u8be5\u8868\u7684\u641c\u7d22\u6761\u4ef6\u65f6\uff0c\u5728`Extra`\u5217\u4e2d\u4f1a\u63d0\u793a\u4e0a\u8ff0\u989d\u5916\u4fe1\u606f\u3002\r\n EXPLAIN SELECT * FROM s1 WHERE common_field = 'a';\r\n\r\n #\u5f53\u4f7f\u7528\u7d22\u5f15\u8bbf\u95ee\u6765\u6267\u884c\u5bf9\u67d0\u4e2a\u8868\u7684\u67e5\u8be2\uff0c\u5e76\u4e14\u8be5\u8bed\u53e5\u7684`WHERE`\u5b50\u53e5\u4e2d\r\n #\u6709\u9664\u4e86\u8be5\u7d22\u5f15\u5305\u542b\u7684\u5217\u4e4b\u5916\u7684\u5176\u4ed6\u641c\u7d22\u6761\u4ef6\u65f6\uff0c\u5728`Extra`\u5217\u4e2d\u4e5f\u4f1a\u63d0\u793a\u4e0a\u8ff0\u989d\u5916\u4fe1\u606f\u3002\r\n EXPLAIN SELECT * FROM s1 WHERE key1 = 'a' AND common_field = 'a';\r\n\r\n #\u5f53\u67e5\u8be2\u5217\u8868\u5904\u6709`MIN`\u6216\u8005`MAX`\u805a\u5408\u51fd\u6570\uff0c\u4f46\u662f\u5e76\u6ca1\u6709\u7b26\u5408`WHERE`\u5b50\u53e5\u4e2d\r\n #\u7684\u641c\u7d22\u6761\u4ef6\u7684\u8bb0\u5f55\u65f6\uff0c\u5c06\u4f1a\u63d0\u793a\u8be5\u989d\u5916\u4fe1\u606f\r\n EXPLAIN SELECT MIN(key1) FROM s1 WHERE key1 = 'abcdefg';\r\n\r\n EXPLAIN SELECT MIN(key1) FROM s1 WHERE key1 = 'UVRySS'; #NlPros \u662f s1\u8868\u4e2dkey1\u5b57\u6bb5\u771f\u5b9e\u5b58\u5728\u7684\u6570\u636e\r\n\r\n SELECT * FROM s1 WHERE key1 = 'abcdefg';\r\n\r\n SELECT * FROM s1 LIMIT 10;\r\n\r\n #\u5f53\u6211\u4eec\u7684\u67e5\u8be2\u5217\u8868\u4ee5\u53ca\u641c\u7d22\u6761\u4ef6\u4e2d\u53ea\u5305\u542b\u5c5e\u4e8e\u67d0\u4e2a\u7d22\u5f15\u7684\u5217\uff0c\u4e5f\u5c31\u662f\u5728\u53ef\u4ee5\r\n #\u4f7f\u7528\u8986\u76d6\u7d22\u5f15\u7684\u60c5\u51b5\u4e0b\uff0c\u5728`Extra`\u5217\u5c06\u4f1a\u63d0\u793a\u8be5\u989d\u5916\u4fe1\u606f\u3002\u6bd4\u65b9\u8bf4\u4e0b\u8fb9\u8fd9\u4e2a\u67e5\u8be2\u4e2d\u53ea\r\n #\u9700\u8981\u7528\u5230`idx_key1`\u800c\u4e0d\u9700\u8981\u56de\u8868\u64cd\u4f5c\uff1a\r\n EXPLAIN SELECT key1,id FROM s1 WHERE key1 = 'a';\r\n\r\n #\u6709\u4e9b\u641c\u7d22\u6761\u4ef6\u4e2d\u867d\u7136\u51fa\u73b0\u4e86\u7d22\u5f15\u5217\uff0c\u4f46\u5374\u4e0d\u80fd\u4f7f\u7528\u5230\u7d22\u5f15\r\n #\u770b\u8bfe\u4ef6\u7406\u89e3\u7d22\u5f15\u6761\u4ef6\u4e0b\u63a8\r\n EXPLAIN SELECT * FROM s1 WHERE key1 > 'z' AND key1 LIKE '%a';\r\n\r\n #\u5728\u8fde\u63a5\u67e5\u8be2\u6267\u884c\u8fc7\u7a0b\u4e2d\uff0c\u5f53\u88ab\u9a71\u52a8\u8868\u4e0d\u80fd\u6709\u6548\u7684\u5229\u7528\u7d22\u5f15\u52a0\u5feb\u8bbf\u95ee\u901f\u5ea6\uff0cMySQL\u4e00\u822c\u4f1a\u4e3a\r\n #\u5176\u5206\u914d\u4e00\u5757\u540d\u53eb`join buffer`\u7684\u5185\u5b58\u5757\u6765\u52a0\u5feb\u67e5\u8be2\u901f\u5ea6\uff0c\u4e5f\u5c31\u662f\u6211\u4eec\u6240\u8bb2\u7684`\u57fa\u4e8e\u5757\u7684\u5d4c\u5957\u5faa\u73af\u7b97\u6cd5`\r\n #\u89c1\u8bfe\u4ef6\u8bf4\u660e\r\n EXPLAIN SELECT * FROM s1 INNER JOIN s2 ON s1.common_field = s2.common_field;\r\n\r\n #\u5f53\u6211\u4eec\u4f7f\u7528\u5de6\uff08\u5916\uff09\u8fde\u63a5\u65f6\uff0c\u5982\u679c`WHERE`\u5b50\u53e5\u4e2d\u5305\u542b\u8981\u6c42\u88ab\u9a71\u52a8\u8868\u7684\u67d0\u4e2a\u5217\u7b49\u4e8e`NULL`\u503c\u7684\u641c\u7d22\u6761\u4ef6\uff0c\r\n #\u800c\u4e14\u90a3\u4e2a\u5217\u53c8\u662f\u4e0d\u5141\u8bb8\u5b58\u50a8`NULL`\u503c\u7684\uff0c\u90a3\u4e48\u5728\u8be5\u8868\u7684\u6267\u884c\u8ba1\u5212\u7684Extra\u5217\u5c31\u4f1a\u63d0\u793a`Not exists`\u989d\u5916\u4fe1\u606f\r\n EXPLAIN SELECT * FROM s1 LEFT JOIN s2 ON s1.key1 = s2.key1 WHERE s2.id IS NULL;\r\n\r\n #\u5982\u679c\u6267\u884c\u8ba1\u5212\u7684`Extra`\u5217\u51fa\u73b0\u4e86`Using intersect(...)`\u63d0\u793a\uff0c\u8bf4\u660e\u51c6\u5907\u4f7f\u7528`Intersect`\u7d22\u5f15\r\n #\u5408\u5e76\u7684\u65b9\u5f0f\u6267\u884c\u67e5\u8be2\uff0c\u62ec\u53f7\u4e2d\u7684`...`\u8868\u793a\u9700\u8981\u8fdb\u884c\u7d22\u5f15\u5408\u5e76\u7684\u7d22\u5f15\u540d\u79f0\uff1b\r\n #\u5982\u679c\u51fa\u73b0\u4e86`Using union(...)`\u63d0\u793a\uff0c\u8bf4\u660e\u51c6\u5907\u4f7f\u7528`Union`\u7d22\u5f15\u5408\u5e76\u7684\u65b9\u5f0f\u6267\u884c\u67e5\u8be2\uff1b\r\n #\u51fa\u73b0\u4e86`Using sort_union(...)`\u63d0\u793a\uff0c\u8bf4\u660e\u51c6\u5907\u4f7f\u7528`Sort-Union`\u7d22\u5f15\u5408\u5e76\u7684\u65b9\u5f0f\u6267\u884c\u67e5\u8be2\u3002\r\n EXPLAIN SELECT * FROM s1 WHERE key1 = 'a' OR key3 = 'a';\r\n\r\n #\u5f53\u6211\u4eec\u7684`LIMIT`\u5b50\u53e5\u7684\u53c2\u6570\u4e3a`0`\u65f6\uff0c\u8868\u793a\u538b\u6839\u513f\u4e0d\u6253\u7b97\u4ece\u8868\u4e2d\u8bfb\u51fa\u4efb\u4f55\u8bb0\u5f55\uff0c\u5c06\u4f1a\u63d0\u793a\u8be5\u989d\u5916\u4fe1\u606f\r\n EXPLAIN SELECT * FROM s1 LIMIT 0;\r\n\r\n #\u6709\u4e00\u4e9b\u60c5\u51b5\u4e0b\u5bf9\u7ed3\u679c\u96c6\u4e2d\u7684\u8bb0\u5f55\u8fdb\u884c\u6392\u5e8f\u662f\u53ef\u4ee5\u4f7f\u7528\u5230\u7d22\u5f15\u7684\u3002\r\n #\u6bd4\u5982\uff1a\r\n EXPLAIN SELECT * FROM s1 ORDER BY key1 LIMIT 10;\r\n\r\n #\u5f88\u591a\u60c5\u51b5\u4e0b\u6392\u5e8f\u64cd\u4f5c\u65e0\u6cd5\u4f7f\u7528\u5230\u7d22\u5f15\uff0c\u53ea\u80fd\u5728\u5185\u5b58\u4e2d\uff08\u8bb0\u5f55\u8f83\u5c11\u7684\u65f6\u5019\uff09\u6216\u8005\u78c1\u76d8\u4e2d\uff08\u8bb0\u5f55\u8f83\u591a\u7684\u65f6\u5019\uff09\r\n #\u8fdb\u884c\u6392\u5e8f\uff0cMySQL\u628a\u8fd9\u79cd\u5728\u5185\u5b58\u4e2d\u6216\u8005\u78c1\u76d8\u4e0a\u8fdb\u884c\u6392\u5e8f\u7684\u65b9\u5f0f\u7edf\u79f0\u4e3a\u6587\u4ef6\u6392\u5e8f\uff08\u82f1\u6587\u540d\uff1a`filesort`\uff09\u3002\r\n\r\n #\u5982\u679c\u67d0\u4e2a\u67e5\u8be2\u9700\u8981\u4f7f\u7528\u6587\u4ef6\u6392\u5e8f\u7684\u65b9\u5f0f\u6267\u884c\u67e5\u8be2\uff0c\u5c31\u4f1a\u5728\u6267\u884c\u8ba1\u5212\u7684`Extra`\u5217\u4e2d\u663e\u793a`Using filesort`\u63d0\u793a\r\n EXPLAIN SELECT * FROM s1 ORDER BY common_field LIMIT 10;\r\n\r\n #\u5728\u8bb8\u591a\u67e5\u8be2\u7684\u6267\u884c\u8fc7\u7a0b\u4e2d\uff0cMySQL\u53ef\u80fd\u4f1a\u501f\u52a9\u4e34\u65f6\u8868\u6765\u5b8c\u6210\u4e00\u4e9b\u529f\u80fd\uff0c\u6bd4\u5982\u53bb\u91cd\u3001\u6392\u5e8f\u4e4b\u7c7b\u7684\uff0c\u6bd4\u5982\u6211\u4eec\r\n #\u5728\u6267\u884c\u8bb8\u591a\u5305\u542b`DISTINCT`\u3001`GROUP BY`\u3001`UNION`\u7b49\u5b50\u53e5\u7684\u67e5\u8be2\u8fc7\u7a0b\u4e2d\uff0c\u5982\u679c\u4e0d\u80fd\u6709\u6548\u5229\u7528\u7d22\u5f15\u6765\u5b8c\u6210\r\n #\u67e5\u8be2\uff0cMySQL\u5f88\u6709\u53ef\u80fd\u5bfb\u6c42\u901a\u8fc7\u5efa\u7acb\u5185\u90e8\u7684\u4e34\u65f6\u8868\u6765\u6267\u884c\u67e5\u8be2\u3002\u5982\u679c\u67e5\u8be2\u4e2d\u4f7f\u7528\u5230\u4e86\u5185\u90e8\u7684\u4e34\u65f6\u8868\uff0c\u5728\u6267\u884c\r\n #\u8ba1\u5212\u7684`Extra`\u5217\u5c06\u4f1a\u663e\u793a`Using temporary`\u63d0\u793a\r\n EXPLAIN SELECT DISTINCT common_field FROM s1;\r\n\r\n #EXPLAIN SELECT DISTINCT key1 FROM s1;\r\n\r\n #\u540c\u4e0a\u3002\r\n EXPLAIN SELECT common_field, COUNT(*) AS amount FROM s1 GROUP BY common_field;\r\n\r\n #\u6267\u884c\u8ba1\u5212\u4e2d\u51fa\u73b0`Using temporary`\u5e76\u4e0d\u662f\u4e00\u4e2a\u597d\u7684\u5f81\u5146\uff0c\u56e0\u4e3a\u5efa\u7acb\u4e0e\u7ef4\u62a4\u4e34\u65f6\u8868\u8981\u4ed8\u51fa\u5f88\u5927\u6210\u672c\u7684\uff0c\u6240\u4ee5\r\n #\u6211\u4eec`\u6700\u597d\u80fd\u4f7f\u7528\u7d22\u5f15\u6765\u66ff\u4ee3\u6389\u4f7f\u7528\u4e34\u65f6\u8868`\u3002\u6bd4\u5982\uff1a\u626b\u63cf\u6307\u5b9a\u7684\u7d22\u5f15idx_key1\u5373\u53ef\r\n EXPLAIN SELECT key1, COUNT(*) AS amount FROM s1 GROUP BY key1;\r\n\r\n #json\u683c\u5f0f\u7684explain\r\n EXPLAIN FORMAT=JSON SELECT * FROM s1 INNER JOIN s2 ON s1.key1 = s2.key2\r\n WHERE s1.common_field = 'a';\r\n\r\n# 7. EXPLAIN\u7684\u8fdb\u4e00\u6b65\u4f7f\u7528\r\n\r\n# 7.1 EXPLAIN\u56db\u79cd\u8f93\u51fa\u683c\u5f0f\r\n# \u8fd9\u91cc\u8c08\u8c08EXPLAIN\u7684\u8f93\u51fa\u683c\u5f0f\u3002EXPLAIN\u53ef\u4ee5\u8f93\u51fa\u56db\u79cd\u683c\u5f0f\uff1a\r\n# \u4f20\u7edf\u683c\u5f0f \uff0c JSON\u683c\u5f0f \uff0c TREE\u683c\u5f0f \u4ee5\u53ca \u53ef\u89c6\u5316\u8f93\u51fa \u3002\u7528\u6237\u53ef\u4ee5\u6839\u636e\u9700\u8981\u9009\u62e9\u9002\u7528\u4e8e\u81ea\u5df1\u7684\u683c\u5f0f\u3002\r\n\r\n# 2. JSON\u683c\u5f0f\r\n\r\n# json\u683c\u5f0f\u7684explain\r\nEXPLAIN FORMAT=JSON SELECT * FROM s1 INNER JOIN s2 ON s1.key1 = s2.key2\r\nWHERE s1.common_field = 'a';\r\n\r\n# 3. TREE\u683c\u5f0f\r\n\r\nEXPLAIN FORMAT=TREE SELECT * FROM s1 INNER JOIN s2 ON s1.key1 = s2.key2\r\nWHERE s1.common_field = 'a';\r\n\r\n# 7.2 SHOW WARNINGS\u7684\u4f7f\u7528\r\n\r\nEXPLAIN SELECT s1.key1, s2.key1 FROM s1 LEFT JOIN s2 ON s1.key1 = s2.key1\r\nWHERE s2.common_field IS NOT NULL;\r\n\r\nSHOW WARNINGS;\r\n\r\nEXPLAIN SELECT * FROM s1 WHERE key1 IN (SELECT key2 FROM s2 WHERE common_field = 'a');\r\n\r\n# 8. \u5206\u6790\u4f18\u5316\u5668\u6267\u884c\u8ba1\u5212\uff1atrace\r\n\r\nSET optimizer_trace=\"enabled=on\",end_markers_in_json=on;\r\n\r\nSET optimizer_trace_max_mem_size=1000000;\r\n\r\nUSE atguigudb1;\r\n\r\nSHOW TABLES;\r\n\r\nSELECT * FROM student WHERE id < 10;\r\n\r\nSELECT * FROM information_schema.OPTIMIZER_TRACE;\r\n\r\n# 9. MySQL\u76d1\u63a7\u5206\u6790\u89c6\u56fe-sys schema\r\n\r\n# 9.2 Sys schema\u89c6\u56fe\u4f7f\u7528\u573a\u666f\r\n\r\n# \u7d22\u5f15\u60c5\u51b5\r\n#1. \u67e5\u8be2\u5197\u4f59\u7d22\u5f15\r\nselect * from sys.schema_redundant_indexes;\r\n#2. \u67e5\u8be2\u672a\u4f7f\u7528\u8fc7\u7684\u7d22\u5f15\r\nselect * from sys.schema_unused_indexes;\r\n#3. \u67e5\u8be2\u7d22\u5f15\u7684\u4f7f\u7528\u60c5\u51b5\r\nselect index_name,rows_selected,rows_inserted,rows_updated,rows_deleted\r\nfrom sys.schema_index_statistics where table_schema='dbname' ;\r\n\r\nSHOW INDEX FROM student_info;\r\n\r\n# \u8868\u76f8\u5173\r\n# 1. \u67e5\u8be2\u8868\u7684\u8bbf\u95ee\u91cf\r\nselect table_schema,table_name,sum(io_read_requests+io_write_requests) as io from\r\nsys.schema_table_statistics group by table_schema,table_name order by io desc;\r\n# 2. \u67e5\u8be2\u5360\u7528bufferpool\u8f83\u591a\u7684\u8868\r\nselect object_schema,object_name,allocated,data\r\nfrom sys.innodb_buffer_stats_by_table order by allocated limit 10;\r\n# 3. \u67e5\u770b\u8868\u7684\u5168\u8868\u626b\u63cf\u60c5\u51b5\r\nselect * from sys.statements_with_full_table_scans where db='dbname';\r\n\r\n# \u8bed\u53e5\u76f8\u5173\r\n#1. \u76d1\u63a7SQL\u6267\u884c\u7684\u9891\u7387\r\nselect db,exec_count,query from sys.statement_analysis\r\norder by exec_count desc;\r\n#2. \u76d1\u63a7\u4f7f\u7528\u4e86\u6392\u5e8f\u7684SQL\r\nselect db,exec_count,first_seen,last_seen,query\r\nfrom sys.statements_with_sorting limit 1;\r\n#3. \u76d1\u63a7\u4f7f\u7528\u4e86\u4e34\u65f6\u8868\u6216\u8005\u78c1\u76d8\u4e34\u65f6\u8868\u7684SQL\r\nselect db,exec_count,tmp_tables,tmp_disk_tables,query\r\nfrom sys.statement_analysis where tmp_tables>0 or tmp_disk_tables >0\r\norder by (tmp_tables+tmp_disk_tables) desc;\r\n\r\n# IO\u76f8\u5173\r\n#1. \u67e5\u770b\u6d88\u8017\u78c1\u76d8IO\u7684\u6587\u4ef6\r\nselect file,avg_read,avg_write,avg_read+avg_write as avg_io\r\nfrom sys.io_global_by_file_by_bytes order by avg_read limit 10;\r\n\r\n# Innodb \u76f8\u5173\r\n#1. \u884c\u9501\u963b\u585e\u60c5\u51b5\r\nselect * from sys.innodb_lock_waits;<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[47],"class_list":["post-1632","post","type-post","status-publish","format-standard","hentry","category-mysql-code","tag-mysql"],"_links":{"self":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1632"}],"collection":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1632"}],"version-history":[{"count":1,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1632\/revisions"}],"predecessor-version":[{"id":1633,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1632\/revisions\/1633"}],"wp:attachment":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1632"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1632"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1632"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}