SQL Query

SQL Query

Here i will give you all sql query which is frequently ask in any interview. Below all queries are most important for interview.

1. How to get nth max salaries ?

select distinct sal from emp e1 
where &n =  (select count(distinct sal) from emp e2 where e1.sal <= e2.sal);

2. How to get nth min salaries ?

select distinct sal from emp e1
where &n =  (select count(distinct sal) from emp e2 where e1.sal >= e2.sal);

3. Find the 3rd MAX salary in the emp table.

select distinct sal from emp e1 
where 3 = (select count(distinct sal) from emp e2 where e1.sal <= e2.sal);

4. Find the 3rd MIN salary in the emp table.

select distinct sal from emp e1 
where 3 = (select count(distinct sal) from emp e2 where e1.sal >= e2.sal);

5. Select FIRST n records from a table.

select * from emp where rownum <= &n;

6. Select LAST n records from a table

select * from emp minus select * from emp 
where rownum <= (select count(*) - &n from emp);

7. How to get 3 Max salaries ?

select distinct sal from emp e1 
where 3 >= (select count(distinct sal) from emp e2 where e1.sal <= e2.sal) order by e1.sal desc;

8. How to get 3 Min salaries ?

select distinct sal from emp e1  
where 3 >= (select count(distinct sal) from emp e2 where e1.sal >= e2.sal);

9. Select DISTINCT RECORDS from emp table.

select * from emp e1
where  rowid = (select max(rowid) from emp e2 where  e1.empno=e2.empno);

10. How to delete duplicate rows in a table ?

delete from emp e1 
where rowid != (select max(rowid) from emp e2 where  e1.empno=e2.empno);

11. Count of number of employees in department wise.

select count(empno), d.deptno, dname from emp e, dept d  
where  e.deptno(+)=d.deptno  group by d.deptno,dname;

12. Suppose there is annual salary information provided by emp table. How to fetch monthly salary of each and every employee?

select ename,sal/12 as monthlysal from emp;

13. Select all record from emp table where deptno =10 or 40.

select * from emp where deptno=30 or deptno=10;

14. Select all record from emp table where deptno=30 and sal>1500.

select * from emp where deptno=30 and sal>1500;

15. Select all record from emp where job not in SALESMAN or CLERK.

select * from emp where job not in ('SALESMAN','CLERK');

16. Select all record from emp where ename in 'BLAKE','SCOTT','KING' and 'FORD'.

select * from emp where ename in('JONES','BLAKE','SCOTT','KING','FORD');

17. Select all records where ename starts with 'S' and its lenth is 6 char.

select * from emp where ename like'S______';

18. Select all records where ename may be any no of character but it should end with 'R'.

select * from emp where ename like'%R';

19. Count MGR and their salary in emp table.

select count(MGR),count(sal) from emp;

20. In emp table add comm+sal as total sal

select ename,(sal+nvl(comm,0)) as totalsal from emp;