1) show databases;
2) use db; 进入到数据库db
3) select database(); --显示当前数据库
4) select "consstr" as colname, t.* from tableName t;
5) select a.id,a.valueA, case (b.valueB is NULL) when 1 then 'z' else b.valueB end from tableA as a left join tableB as b on(id);
6)导入.sql脚本：
在命令行下：mysql -h *** -u *** -p <***.sql
进入到mysql,在mysql>命令行下： source **.sql
7)在mysql中可以让查询结果的每行竖排列，只需要用\G代替查询语句末尾的分号即可。如：
select * from test limit 10 \G
8)show tables like '%name%';
9) 查看建表语句：show create table tablename ;
10) 删除主键: alter table tablename drop primary key;
11) 导出数据:
select * from table into outfile 'fileName' ; --只能在本机导出。
mysqldump -h host -u user -ppwd database table > file
12) 导入数据:
load data infile 'filepath' into table tableName;
mysqldump ...
