MySQL性能优化---定位慢查询

##查询慢查询时间,mysql默认10s
SHOW VARIABLES LIKE ‘long_query_time‘;

##查询慢查询的次数
SHOW STATUS LIKE ‘slow_queries‘;

SHOW VARIABLES LIKE ‘log_queries_%‘

##修改OFF值为ON
SET GLOBAL log_queries_not_using_indexes=ON;
##再次查看
SHOW VARIABLES LIKE ‘log_queries_%‘

SET GLOBAL long_query_time=0.9;
##重启查看慢查询时间
SHOW VARIABLES LIKE ‘long_query_time‘;

SHOW VARIABLES LIKE ‘slow_query_log‘;

SET GLOBAL slow_query_log=ON;
##再次查看
SHOW VARIABLES LIKE ‘slow_query_log‘;

SHOW VARIABLES LIKE ‘slow_query_log_file‘;

SET GLOBAL slow_query_log_file=‘E:\\mysqlerror.log‘

/*部门表*/
CREATE TABLE dept( 
deptno MEDIUMINT   UNSIGNED  NOT NULL  DEFAULT 0,  /*编号*/
dname VARCHAR(20)  NOT NULL  DEFAULT "", /*名称*/
loc VARCHAR(13) NOT NULL DEFAULT "" /*地点*/
) ENGINE=MYISAM DEFAULT CHARSET=utf8 ;

/*员工表*/
CREATE TABLE emp
(empno  MEDIUMINT UNSIGNED  NOT NULL  DEFAULT 0, /*编号*/
ename VARCHAR(20) NOT NULL DEFAULT "", /*名字*/
job VARCHAR(9) NOT NULL DEFAULT "",/*工作*/
mgr MEDIUMINT UNSIGNED NOT NULL DEFAULT 0,/*上级编号*/
hiredate DATE NOT NULL,/*入职时间*/
sal DECIMAL(7,2)  NOT NULL,/*薪水*/
comm DECIMAL(7,2) NOT NULL,/*红利*/
deptno MEDIUMINT UNSIGNED NOT NULL DEFAULT 0 /*部门编号*/
)ENGINE=MYISAM DEFAULT CHARSET=utf8 ;

/*薪水*/
CREATE TABLE salgrade
(
grade MEDIUMINT UNSIGNED NOT NULL DEFAULT 0,
losal DECIMAL(17,2)  NOT NULL,
hisal DECIMAL(17,2)  NOT NULL
)ENGINE=MYISAM DEFAULT CHARSET=utf8;

#测试数据leveof
INSERT INTO salgrade VALUES (1,700,1200);
INSERT INTO salgrade VALUES (2,1201,1400);
INSERT INTO salgrade VALUES (3,1401,2000);
INSERT INTO salgrade VALUES (4,2001,3000);
INSERT INTO salgrade VALUES (5,3001,9999);

DELIMITER $$
        CREATE FUNCTION rand_string(n INT) 
        RETURNS VARCHAR(255) #该函数会返回一个字符串
        BEGIN 
        #chars_str定义一个变量 chars_str,类型是 varchar(100),默认值‘abcdefghijklmnopqrstuvwxyzABCDEFJHIJKLMNOPQRSTUVWXYZ‘;
         DECLARE chars_str VARCHAR(100) DEFAULT
           ‘abcdefghijklmnopqrstuvwxyzABCDEFJHIJKLMNOPQRSTUVWXYZ‘;
         DECLARE return_str VARCHAR(255) DEFAULT ‘‘;
         DECLARE i INT DEFAULT 0;
         WHILE i < n DO 
           SET return_str =CONCAT(return_str,SUBSTRING(chars_str,FLOOR(1+RAND()*52),1));
           SET i = i + 1;
           END WHILE;
          RETURN return_str;
          END $$  

DELIMITER $$
        CREATE FUNCTION rand_num()
        RETURNS INT(5)
        BEGIN
         DECLARE i INT DEFAULT 0;
         SET i =FLOOR(10+RAND()*500);
         RETURN i;
        END $$

DELIMITER $$
        CREATE PROCEDURE insert_emp(IN START INT(10),IN max_num INT(10))
        BEGIN
        DECLARE i INT DEFAULT 0; 
        #set autocommit =0 把autocommit设置成0
         SET autocommit = 0;  
         REPEAT
         SET i = i + 1;
         INSERT INTO emp VALUES ((START+i) ,rand_string(6),‘SALESMAN‘,0001,CURDATE(),2000,400,rand_num());
          UNTIL i = max_num
         END REPEAT;
           COMMIT;
         END $$

CALL insert_emp (100001,40000000);  

SELECT * FROM emp WHERE empno=10005