常用查询及连接查询的使用select * from student where id=1;

Question

常用查询及连接查询的使用select * from student where id=1;

Answer 1

（一）条件查询 where
1.等值查询 =

select * from student where id=1;

2.不等值查询 != (< >)

查询年龄不是20岁的学生信息

select * from student where age!=20;

3.关系比较查询 < <= > >=

查询年龄大于20岁的学生信息

select * from student where age>20;

4.逻辑运算查询 and or

and 满足所有条件 or只需要满足其中一个条件

查询年龄小于21岁并且住址是郑州

select * from student where age<21 and address="郑州";

查询年龄小于21岁或者住址是郑州的

select * from student where age<21 or address="郑州";

5.区间查询 between .. and (包含边界值)

查询年龄是18岁到21岁之间

select * from student where age between 18 and 21;

select * from student where age>=18 and age<=21;

6.模糊查询 like

① %（匹配0-n个字符）

查询学生表中名字包含x的学生信息

select * from student where stuname like '%x%';

② _ （匹配一个字符,相当于一个占位符）

查询学生表中地址第二个字为京的信息

select * from student where adderss like '_京';