Oracle数据库的基本用法
时间：2021-07-01 10:21:17
帮助过：24人阅读
1. select *
from emp;
--
选取指定列的内容
select job
from emp;
select ename,sal
from emp;
--
条件判断
select sal
from emp
where sal=
800;
--
between and 方法
select *
from emp
where sal between
2000 and
3000;
--
嵌套的使用
select job
from
(select *
from emp
where sal between
2000 and
3000);
--
单列数据的改变
select sal+
25 from emp;
--用like(模糊)概念 （-一个字符） （%
0个或多个字符）
select job
from emp
where job like
‘%LE%‘;
--
从in（）里面的数据选出
select *
from emp
where comm
in(
300,
500);
select sal,sal+
25.00 AS saly
from emp;
--
字符串的连接 AS别名 将job换成ta
select empno,empno+
25||
‘is a ‘||job AS ta
from emp;
--
删除重复行 关键词DISTINCT
select DISTINCT comm
from emp;
--
用IS NULL 关键字判断为空的情况
select *
from emp
where comm IS NULL;
select comm
from emp
where comm IS NULL;
二、优先级
1 算术运算符
2 连接符
3 比较符
4 IS [NOT] NULL, LIKE, [NOT] IN
5 [NOT] BETWEEN
6 NOT
7 AND
8 OR
Oracle数据库的基本用法
标签：color 5.0 判断为空 tin from 关键字 class 优先级 取整
