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SQL中的一些算术表达式

Sophia的玲珑阁 2022-03-15 阅读 58

1.使用least()和greatest()寻找其中的最小值和最大值

如:

select least('a','b','p'),greatest ('a','b','p')
from dual;

可得:

2.表示区间选择的语法可以使用between...and 语句 如:

select employee_id ,last_name ,salary 
from employees e 
where salary between 6000 and 8000;

select employee_id ,last_name ,salary 
from employees e 
where salary <6000 or salary >8000;-- 不在6000和8000

3. in 在内    not in 不在内 如:

select last_name ,salary ,department_id 
from employees e 
where department_id in(10,20,30);

select last_name ,salary ,department_id 
from employees e 
where department_id not in(10,20,30);

4. like代表模糊查询。

#like:模糊查询
select last_name 
from employees e 
where last_name like '%a%';-- %代表不确定字数的字符

select last_name 
from employees e 
where last_name like 'a%';-- a开头的字符

select last_name 
from employees e 
where last_name like '_a%';-- 第二个字符a

5.

#escape可以定义转义字符

#regexp\rlike正则表达式

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