1. 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);
  2. 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);
  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 e2where 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. 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;

  8. 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.sal desc;
  9. 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);
  10. 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);
  11. Select DISTINCT RECORDS from emp table.
    select * from emp a where  rowid = (select max(rowid) from emp b where  a.empno=b.empno);
  12. 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);
  13. 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;
  14.  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;
  15. Select all record from emp table where deptno =10 or 40.select * from emp where deptno=30 or deptno=10;
  16. Select all record from emp table where deptno=30 and sal>1500.select * from emp where deptno=30 and sal>1500;
  17. Select  all record  from emp where job not in SALESMAN  or CLERK.select * from emp where job not in (‘SALESMAN’,’CLERK’);
  18. Select all record from emp where ename in ‘BLAKE’,’SCOTT’,’KING’and’FORD’.select * from emp where ename in(‘JONES’,’BLAKE’,’SCOTT’,’KING’,’FORD’);
  19. Select all records where ename starts with ‘S’ and its lenth is 6 char.select * from emp where ename like’S____’;
  20. Select all records where ename may be any no of  character but it should end with ‘R’.select * from emp where ename like’%R’;
  21. Count  MGR and their salary in emp table.select count(MGR),count(sal) from emp;
  22. In emp table add comm+sal as total sal  .select ename,(sal+nvl(comm,0)) as totalsal from emp;
  23. Select  any salary <3000 from emp table. select * from emp  where sal> any(select sal from emp where sal<3000);
  24. Select  all salary <3000 from emp table. select * from emp  where sal > all(select sal from emp where sal<3000);
  25. Select all the employee  group by deptno and sal in descending order.select ename,deptno,sal from emp order by deptno,sal desc;
  26. How can I create an empty table emp1 with same structure as emp?Create table emp1 as select * from emp where 1=2;
  27. How to retrive record where sal between 1000 to 2000?Select * from emp where sal between 1000 and 2000;
  28. Select 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)
  29. 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)
  30. How to fetch only common records from two tables emp and emp1?(Select * from emp) Intersect (Select * from emp1)
  31.  How can I retrive all records of emp1 those should not present in emp2?(Select * from emp1) Minus (Select * from emp2)
  32. Count the totalsal  deptno wise where more than 2 employees exist.SELECT  deptno, sum(sal) As totalsal

    FROM emp

    GROUP BY deptno

    HAVING COUNT(empno) > 2