条件查询

elect … from 表名 where …

比较运算符

>

查询大于18岁的信息

select * from students where age>18;

select id,name,gender from students where age>18;

<

查询小于18岁的信息

select * from students where age<18;

>= <=

查询小于或等于18岁的信息

=

查询年龄为18岁的所有学生的名字

select * from students where age=18;

!= 或者 <>

逻辑运算符

and

18到28岁之间所有学生的信息

select * from students where age>18 and age<28;

失败select * from students where age>18 and <28;

18岁以上的女性

select * from students where age>18 and gender=“女”;

select * from students where age>18 and gender=2;

or

18岁以上或者身高查过180(包含)以上

select * from students where age>18 and height>=180;

not

不在 18岁以上的女性 这个范围内的信息

select * from students where not age>18 and gender=2;

select * from students where not (age>18 and gender=2);

年龄不是小于或者等于18 并且是女性

select * from students where (not age<=18) and gender=2;

模糊查询

like

% 替换1个或者多个

_ 替换1个

查询姓名中 以 “小” 开始的名字

select name from students where name=“小”;

select name from students where name like “小%”;

查询姓名中 有"小" 所有的名字

select name from students where name like “%小%”;

查询有2个字的名字

select name from students where name like “__”;

查询有3个字的名字

select name from students where name like “___”;

查询至少有2个字的名字

select name from students where name like “__%”;

rlike 正则

查询以 周开始的姓名

select name from students where name rlike “^周.*”;

查询已 周开始、伦结尾的姓名

select name from students where name rlike “^周.*伦$”;

范围查询 in(1, 3，8 )表示在一个非连续的范围内

查询 年龄为18、34的名字

select name,age from students where age=18 or age=34;

select name,age from students where age=18 or age=34 or age=12;

select name,age from students where age in (12, 18, 34);

not in 不非连续的范围之内

年龄不是 18、34岁之间的信息

select name,age from students where age not in (12, 18, 34);

between … and …表示在一个连续的范围内

查询 年龄在18到34之间的信息

select name,age from students where age between 18 and 34;

not between … and …表示不在一个连续的范围内

查询 年龄不在在18到34之间的的信息

select * from students where age not between 18 and 34;

select * from students where not age between 18 and 34;

失败的select * from students where age not (between 18 and 34);