搜索所有

select * from user_form

查询多列

select id,name,age from user_form

查询结果去重

select distinct university from user_form

查询结果限制返回行数

select age from user_form limit 2

查询到结果重新命名

select name as user_name from user_form 

查询有一个限制条件

select name from user_form where age=25
select name from user_form where age>20
select name from user_form where age!=25

查询区间限制的结果

select name from user_form where age>20 and age<25
select name from user_form where age between 21 and 24

where过滤空值

select name from user_form where university is not null

查询有多个限制条件

select name from user_form where age>20 and university='123'
select name from user_form where age>20 or university='123'
select name from user_form where age in(10,20,22)
select name from user_form where (age=20 and university='111')or(age>12 and university='222')

查询某一字段包含某字符串

select name from user_form where university like "%北京%"
select name from user_form where university regexp "北京"

查询最大值

select max(age) from user_form

查询数量

select count(age) from user_form where age=20

查询平均值-round(a,b)b为保留几位小数

select round(avg(age),2) from user_form where university='222'

分组按条件查询

select gender,age,count(gender) from user_form group by gender,age

分组过滤查询

select gender,avg(age) as avg_age from user_form group by gender having avg_age>20

分组排序查询

select gender,avg(age) as avg_age from user_form group by gender order by avg_age

查询两表关联信息

select a.name,age 
from user_info as a,user_detail as b 
where a.name=b.name and b.university='123'