SQL必知必会

检索单列
select pro_id
form products；
检索多列
select pro_id,pro_name,pro_price
form products；
检索所有列
select *
form products;

按单列排序
select pro_name
from products
order by pro_name;
按多列排序
select pro_name,pro_id,pro_price
from products
order by pro_price,pro_name;
按位置排序(select清单中的相对位置)
selcet pro_id,pro_price,pro_name
from products
order by 2,3;
指定排序方向(默认为升序asc,降序为desc)
select pro_id,pro_name,pro_price
from products
order by pro_price desc,pro_name

检查单个值
select pro_name,pro_price
from products
where pro_price = 10;
不匹配检查
select vend_id,pro_name
from products
where vend_id != ‘Dl001’
范围值检查
select pro_price,pro_name
from products
where pro_price between 5 and 10;
空值检查(NULL)
select pro_name
from products
where pro_price is null；

=           等于                           
!=   <> 不等于 
<           小于 
<=         小于等于 
!<          不小于
>           大于
>=         大于等于
!>          不大于
between  在两个值之间
is null     为空值   
and        与
or           或
in           在
not         非
()           用括号表示优先级

使用and or ()操作符
select pro_name,pro_price
from products
where (vend_id =‘dl001‘ or vend_id=‘bs001‘) and pro_price > 10;
使用 in 操作符
select pro_name,pro_price
from products
where vend_id in (‘dl001‘,‘sa001‘)
order by pro_name;
使用not 操作符
select pro_name
from products
where not vend_id = ‘dl001‘
order by pro_name;