MySQL学习5:查询拓展与排序

Posted 2021-08-31 Z|Star

模糊查询

一般查询

关键词:like
% 替换1个或者多个
_ 替换一个

案例:
1.查询姓名中以"小"开始的名字

select name from students where name like "小%";

2.查询姓名中有2个字的名字

select name from students where name like "__";

3.查询姓名中有至少有2个字的名字

select name from students where name like "__%";

正则查询

关键词:rlike
案例:
1.查询以章开始的姓名

 select name from students where name rlike "^章.*";

范围查询

非连续范围

关键词:in 表示在一个非连续的范围内
案例:
1.查询 年龄为18,34的姓名

select name from students where age in (18,34);
--等价于
select name from students where age=18 or age=34;

连续范围

关键词:between and 表示在一个连续的范围内
案例:
1.查询年龄在18到34之间的姓名

select name from students where age between 18 and 34;

空判断

关键词:null
不区分大小写
案例:
1.查询身高为空的姓名

select name from students where height is NULL;

升序排序

关键词: order by … asc
案例:
1.查询所有信息,按照年龄从小到大排序

select * from students order by age asc;

2.查询所有信息,按照年龄从小到大,身高从小到大排序

select * from students order by age asc, height asc;

降序排序

关键词: order by … desc
案例:
1.查询所有信息,按照年龄从大到小排序

select * from students order by age desc;