Complex Queries in SQL ( Oracle )

To fetch ALTERNATE records from a table. (EVEN NUMBERED)select * from emp where rowid in (select decode(mod(rownum,2),0,rowid, null) from emp);

To select ALTERNATE records from a table. (ODD NUMBERED)select * from emp where rowid in (select decode(mod(rownum,2),0,null ,rowid) from emp);

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);

Find the 3rd MIN salary in the emp table.select distinct sal from emp e1 where 3 = (select count(distinct sal) from emp e2where e1.sal >= e2.sal);

Select FIRST n records from a table.select * from emp where rownum<= &n;

Select LAST n records from a tableselect * from emp minus select * from emp where rownum<= (select count(*) - &n from emp);

List dept no., Dept name for all the departments in which there are no employees in the department.select * from dept where deptno not in (select deptno from emp);

alternate solution: select * from dept a where not exists (select * from emp b where a.deptno = b.deptno);

altertnate solution: select empno,ename,b.deptno,dname from emp a, dept b where a.deptno(+) = b.deptno and empno is null;

How to get 3 Max salaries ?select distinct sal from emp a where 3 >= (select count(distinct sal) from emp b where a.sal<= b.sal) order by a.saldesc;

How to get 3 Min salaries ?select distinct sal from emp a where 3 >= (select count(distinct sal) from emp b where a.sal>= b.sal);

How to get nth max salaries ?

select distinct hiredate from emp a where &n = (select count(distinct sal) from emp b where a.sal>= b.sal);

Select DISTINCT RECORDS from emp table.select * from emp a where rowid = (select max(rowid) from emp b where a.empno=b.empno);

How to delete duplicate rows in a table?delete from emp a where rowid != (select max(rowid) from emp b where a.empno=b.empno);

Count of number of employees in department wise.select count(EMPNO), b.deptno, dname from emp a, dept b where a.deptno(+)=b.deptno group by b.deptno,dname;

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

selectename,sal/12 as monthlysal from emp;

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

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

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

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

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

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

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

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

select * from emp where enamelike'S____';

Select all records where ename starts with â€˜Sâ€™ and its lenth is 6 char.

select * from emp where enamelike'%R';

Select all records where ename may be any no of character but it should end with â€˜Râ€™.

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

Count MGR and their salary in emp table.

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

In emp table add comm+sal as total sal .

select * from emp where sal> any(select sal from emp where sal<3000);

Select any salary <3000 from emp table.

select * from emp where sal> all(select sal from emp where sal<3000);

Select all salary <3000 from emp table.

selectename,deptno,sal from emp order by deptno,saldesc;

Select all the employee group by deptno and sal in descending order.

Create table emp1 as select * from emp where 1=2;

How can I create an empty table emp1 with same structure as emp?

How to retrive record where salbetween 1000 to 2000?

Select * from emp where sal>=1000 And sal<2000Select all records where dept no of both emp and dept table matches.

select * from emp where exists(select * from dept where emp.deptno=dept.deptno)If there are two tables emp1 and emp2, and both have common record. How can I fetch all the recods but common records only once?

(Select * from emp) Union (Select * from emp1)How to fetch only common records from two tables emp and emp1?

(Select * from emp) Intersect (Select * from emp1)How can I retrive all records of emp1 those should not present in emp2?

(Select * from emp) Minus (Select * from emp1)Count the totalsa deptno wise where more than 2 employees exist.

SELECT deptno, sum(sal) As totalsal

FROM emp

GROUP BY deptno

HAVING COUNT(empno) > 2