1 select * from tab;

1 select * from user_tables;

1 select field1,filed2,.. .
2 from tablename
3 [where condition];

 1 -- 查询所有员工的名字和雇员号
 2 select empno,ename from emp;
 3 
 4 -- 查询所有员工的雇员号、姓名、岗位
 5 select empno,ename,job from emp;
 6 
 7 -- 字段的别名 as
 8 select ename as "姓名" from emp;
 9 select ename as "姓名",job as "岗位" from emp;
10 
11 -- 别名一定要用双引号,不能用单引号
12 select ename "姓名",job "岗位" from emp;
13 -- 双引号可以省略
14 select ename 姓名 from emp;
15 
16 -- 表的别名
17 select emp.ename,emp.job from emp;
18 select e.ename,e.job from emp e;

1 -- 查询公司的工种
2 select distinct e.job
3 from emp e;

 1 -- 把部分10的雇员查询出来
 2 select * 
 3 from emp 
 4 where deptno = 10;
 5 
 6 -- 把名称为smith的雇员
 7 select e.*
 8 from emp e
 9 where e.ename = 'SMITH';
10 
11 -- 查询底薪大于等于1000的员工
12 select e.*
13 from emp e
14 where e.sal >= 1000;
15 
16 select e.*
17 from emp e
18 where e.sal <> 800

1 -- 查询薪资大于 800 的雇员
2 select e.*
3 from emp e
4 where e.sal > some(1000,800);
5 
6 -- 查询薪资大于 1000
7 select e.*
8 from emp e
9 where e.sal > all(1000,800);

1 -- 查询没有津贴的雇员
2 select e.*
3 from emp e
4 where e.comm is null；
5 
6 -- 查询有津贴的雇员
7 select e.*
8 from emp e
9 where e.comm is not null；

1 -- 查询薪资在1000-5000之间的雇员
2 select e.*
3 from emp e
4 where e.sal between 1000 and 5000；

 1 -- 查询部门号是10和20的员工
 2 select e.*
 3 from emp e
 4 where e.deptno in(10,20);
 5 
 6 -- 查询部门号不是10和20的员工
 7 select e.*
 8 from emp e
 9 where e.deptno not in(10,20);
10 
11 -- 查询薪资是1000,2000,5000的员工
12 select e.*
13 from emp e
14 where e.sal in (1000,2000,5000);

 1 -- 查询名字是c开头的雇员
 2 select e.*
 3 from emp e
 4 where e.ename like 'c%';
 5 
 6 -- 查询名字中第二个字母是M的雇员
 7 select e.*
 8 from emp e
 9 where e.ename like '_M%'
10 
11 -- 查询名字中含有M的雇员
12 select e.*
13 from emp e
14 where e.ename like '%M%';
15 
16 -- 查询名字中含有%的雇员
17 select e.*
18 from emp e
19 where e.ename like '%\%%' escape('\');

 1 -- 查询部门10且薪资大于等2000的雇员
 2 select e.*
 3 from emp e
 4 where e.deptno = 10 and e.sal >= 2000;
 5 
 6 -- 查询名字中含M且薪资大于1000的雇员
 7 select e.*
 8 from emp e
 9 where e.ename like '%M%' and e.sal > 1000
10 
11 -- 查询部门在10或20的雇员
12 select e.*
13 from emp e
14 where e.deptno = 10 or e.deptno = 20

1 select e.ename,e.sal,e.deptno
2 from emp e
3 where e.deptno in 
4 (
5 select d.deptno
6 from dept d
7 where d.dname = 'SALES' or d.dname = 'RESEARCH'
8 );

1 -- 查询出每个雇员的月薪(收入)
2 select e.ename,e.sal+e.comm as "收入",e.deptno
3 from emp e；

1 -- nvl函数优化
2 select e.ename,e.sal+nvl(e.comm,0) "收入",e.deptno
3 from emp e；