Oracle查询

条件查询？

1.select * from emp where sal>1500;

2.select * from emp where comm is not null; //可以得到奖金的人员所有信息

3.select * from emp where sal>1500 and comm is not noll; //薪水大于1500而且有奖金

4.select * from emp where not (sal>1500 and comm is not null);

5.select * from emp where sal between 1500 and 3000;

6.select * from emp where sal >=1500 and sal <=3000;

7.select * from emp where hibedate between '1-1 月-81' and '31-12月 -81' ;

8.select * from emp where ename = 'SIMITH' ; //注意oracle对字符串大小写敏感

9.select * from emp where empno=7366 or empno=7369 ;

10.select * from emp where empno in (7366,7369) ;

11.select * from emp where empno not in (7369,7366) ;

子查询?

1.查询薪水最高的员工的名子，薪水

select ename ,sal from emp where sal= (select max(sal) from emp) ;

2.高于平均值的员工

select ename,sal from emp where sal > (select avg(sak) from emp);

3.第个部门里，工资最高的员工

select ename,sal from emp jion (select max(sal) max_sal,deptno from emp group by deptno) t

on (emp.sal = t.max_sal and emp.dept.no=t.deptno) ;

4.每个部门平均工资,这个工资的等级

5.自连接

select e1.ename,e2.ename from emp e1,emp e2 where e1.mgr = e2.empno;

表连接(连表查询)?

1.select ename,dname from emp,dept where emp.deptno=dept.deptno ; // (SQL1992)

2.select ename,dname, from emp join dept on (emp.deptno=dept.deptno); // (SQL1999)

3.select ename,dname, from emp join dept using (deptno) ; // (不推荐)

4.select ename,grade from emp e,jion salgrade s on (e.sal between s.losal and s.hisal) ;

6.select ename,dname,grade from

emp e join dept d on (e.deptno=d.deptno)

jion salgrade s on (e.sal between s.losal and s.hisal)

where ename not like ‘_A%’ ;

7.select e1.ename,e2.ename from emp e1 join emp e2 on (e1.mgr = e2.empno) ;(自连接)

8.select e1.ename,e2.ename from emp e1 left outer jion emp e2 on (e1.mgr=e2.empno) ;(左处连接)

9.select e1.ename,e2.ename from emp e1 right outer jion emp e2 on (e1.mgr=e2.empno) ;(右处连接)

10.select e1.ename,e2.ename from emp e1 full jion emp e2 on (e1.mgr=e2.empno) ;(左右处连接)

11.求部门中哪些人的工资最高

select ename,sal from emp

join (select max(sal) max_sal,deptno from emp group by deptno) t

on (emp.sal = t.max_sal and emp.deptno = t.deptno)

12.求部门平均工资的等级

select deptno,avg_sal, grad from

(select deptno,avg(sal) avg_sal from emp group by deptno) t

join salgrade s on (t.avg_sal betwen s.losal and s.hisal);

常用系统查询命令？

1.当前用户下有多少张表,oracle默认的表user_tables· select table_name from user_tables;

· select * from tab;

2.当前用户下有多少个视图；

select view_name from user_views ;

3.查询当前数据库名；

select name from v$database;

4.查询当前数据库实例名：

select instance_name from v$instance;

5.当前用户下有多少个约束；

select constraint_name from user_constraints ;