Mysql常用查询

摘自：https://blog.csdn.net/weixin_41189380/article/details/83375281

Mysql常用查询

1. 单表查询

查询一张表：select * from table;

查询指定字段：select  c1, c2, c3 from table;

where条件查询：select c1, c2, c3 from table where id=1;(>, <, >=, <=... ...)

带in关键字：select c1, c2 from table where age in (21, 23);

带between and的范围查询：select  c1, c2 from table where age between 21 and 29;

带like的模糊查询：select c1, c2 from table where like 'Wshile'; (Wshile%, %Wshile%)

空值查询： select c1 from table where name is(not) null;

带and的多条件查询：select * from table where gname='一年级' and age=23;

带or的多条件查询：select * frome t_student where gradeName=’一年级’ or age=23；//或者，条件只要满足一个

distinct去除重复查询：select destinct c1 from table;

对查询结果order by：select * frome t_student order by age desc；//降序，从大到小，不加desc默认为升序

分组查询group by：select gradeName,count(stuName) from t_student group by gradeName;

2. 多表连接查询

表一：t_book

 表二：t_bookType