mhbsoft的博客

7种组合方式：SELECT * FROM mhbtest.dept a inner JOIN mhbtest.emp b on a.deptno = b.deptidSELECT * FROM mhbtest.dept a LEFT JOIN mhbtest.emp b on a.deptno = b.deptidSELECT * FROM mhbtest.dept a RIGHT JOIN mhbtest.emp b on a.deptno = b.deptidSELECT * FROM m

查看 profile 状态：show variables like 'profiling'设置 profile 状态：set profiling = off // 使用后没啥反映 希望有大佬解释一下查看部分执行记录：show PROFILES查看固定记录的执行情况：下面代表的是 71 条执行记录，show profile cpu,block io for QUERY 71;...

创建表：CREATE TABLE `mhbtest`.`dept` ( `id` int(10) NOT NULL AUTO_INCREMENT, `deptno` int(11) NULL DEFAULT NULL, `dname` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL, `loc` varchar(255) CHARACTER SET utf8 COLLATE utf8_ge

show VARIABLES like '%slow_query_log%'上图ON，需要关闭的话：set GLOBAL slow_query_log = 0 // 关闭执行：set GLOBAL slow_query_log = 1 // 开启

1. 新建表中添加索引① 普通索引create table t_dept( no int not null primary key, name varchar(20) null, sex varchar(2) null, info varchar(20) null, index index_no(no) )② 唯一索引create table t_dept( no int not null primary key, name