distinct 去重（查询行是否重复）
例
select distinct age,name from pserson;
>>> | age | name |
>>> | 18 | Jon |
>>> | 19 | Tom |
>>> | 18 | Tom |
as 替换字段名
select name as 姓名,age from pserson where name='Tom';
>>> | 姓名 | age |
>>> | Tom | 19 |
>>> | Tom | 18 |
- 表名也可以用
as替换
<小于 >大于 =等于 >=大于等于 <=小于等于 !=或 <>不等于-- 比较运算符
select * from pserson where age = 18;
逻辑运算符and or not
select * from pserson where age >= 18 and name='Tom' ;
like 模糊查询
%匹配任意个_匹配一个
匹配开头
select * from pserson where name like 'T%';
匹配开头并且之后只有一个
select * from pserson where name like 'T_';
匹配包含
select * from pserson where name like '%T%';
至少匹配两个
select * from pserson where name like '__%';
rlike 正则查询
匹配开头
select * from pserson where name like '^T.*';
匹配结尾
select * from pserson where name like '.*T$';
in非连续范围内 not in不非连续范围内（非连续范围外） between...and...连续范围内 not between...and...连续范围外 -- 范围查询
select * from pserson where name in ('Tom', 'Marry');
select * from pserson where name not in ('Tom', 'Marry');
select * from pserson where id between 3 and 8;
select * from pserson where id not between 3 and 8;
is null空判断 is not null 非空判断
select * from pserson where name is null;
