Tuesday, April 6, 2010

practice exercises on Sql

II . SCHEMA :

Table 1 : DEPT

DEPTNO (NOT NULL , NUMBER(2)), DNAME (VARCHAR2(14)),

LOC (VARCHAR2(13)

Table 2 : EMP

EMPNO (NOT NULL , NUMBER(4)), ENAME (VARCHAR2(10)),

JOB (VARCHAR2(9)), MGR (NUMBER(4)), HIREDATE (DATE),

SAL (NUMBER(7,2)), COMM (NUMBER(7,2)), DEPTNO (NUMBER(2))

MGR is the empno of the employee whom the employee reports to. DEPTNO is a foreign key.

QUERIES

1. List all the employees who have at least one person reporting to them.

2. List the employee details if and only if more than 10 employees are present in department no 10.

3. List the name of the employees with their immediate higher authority.

4. List all the employees who do not manage any one.

5. List the employee details whose salary is greater than the lowest salary of an employee belonging to deptno 20.

6. List the details of the employee earning more than the highest paid manager.

7. List the highest salary paid for each job.

8. Find the most recently hired employee in each department.

9. In which year did most people join the company? Display the year and the number of employees.

10. Which department has the highest annual remuneration bill?

11. Write a query to display a ‘*’ against the row of the most recently hired employee.

12. Write a correlated sub-query to list out the employees who earn more than the average salary of their department.

13. Find the nth maximum salary.

14. Select the duplicate records (Records, which are inserted, that already exist) in the EMP table.

15. Write a query to list the length of service of the employees (of the form n years and m months).

KEYS:

1. SELECT DISTINCT(A.ENAME) FROM EMP A, EMP B WHERE A.EMPNO = B.MGR; or SELECT ENAME FROM EMP WHERE EMPNO IN (SELECT MGR FROM EMP);

2. SELECT * FROM EMP WHERE DEPTNO IN (SELECT DEPTNO FROM EMP GROUP BY DEPTNO HAVING COUNT(EMPNO)>10 AND DEPTNO=10);

3. SELECT A.ENAME "EMPLOYEE", B.ENAME "REPORTS TO" FROM EMP A, EMP B WHERE A.MGR=B.EMPNO;

4. SELECT * FROM EMP WHERE EMPNO IN ( SELECT EMPNO FROM EMP MINUS SELECT MGR FROM EMP);

5. SELECT * FROM EMP WHERE SAL > ( SELECT MIN(SAL) FROM EMP GROUP BY DEPTNO HAVING DEPTNO=20);

6. SELECT * FROM EMP WHERE SAL > ( SELECT MAX(SAL) FROM EMP GROUP BY JOB HAVING JOB = 'MANAGER' );

7. SELECT JOB, MAX(SAL) FROM EMP GROUP BY JOB;

8. SELECT * FROM EMP WHERE (DEPTNO, HIREDATE) IN (SELECT DEPTNO, MAX(HIREDATE) FROM EMP GROUP BY DEPTNO);

9. SELECT TO_CHAR(HIREDATE,'YYYY') "YEAR", COUNT(EMPNO) "NO. OF EMPLOYEES" FROM EMP GROUP BY TO_CHAR(HIREDATE,'YYYY') HAVING COUNT(EMPNO) = (SELECT MAX(COUNT(EMPNO)) FROM EMP GROUP BY TO_CHAR(HIREDATE,'YYYY'));

10. SELECT DEPTNO, LPAD(SUM(12*(SAL+NVL(COMM,0))),15) "COMPENSATION" FROM EMP GROUP BY DEPTNO HAVING SUM( 12*(SAL+NVL(COMM,0))) = (SELECT MAX(SUM(12*(SAL+NVL(COMM,0)))) FROM EMP GROUP BY DEPTNO);

11. SELECT ENAME, HIREDATE, LPAD('*',8) "RECENTLY HIRED" FROM EMP WHERE HIREDATE = (SELECT MAX(HIREDATE) FROM EMP) UNION SELECT ENAME NAME, HIREDATE, LPAD(' ',15) "RECENTLY HIRED" FROM EMP WHERE HIREDATE != (SELECT MAX(HIREDATE) FROM EMP);

12. SELECT ENAME,SAL FROM EMP E WHERE SAL > (SELECT AVG(SAL) FROM EMP F WHERE E.DEPTNO = F.DEPTNO);

13. SELECT ENAME, SAL FROM EMP A WHERE &N = (SELECT COUNT (DISTINCT(SAL)) FROM EMP B WHERE A.SAL<=B.SAL);

14. SELECT * FROM EMP A WHERE A.EMPNO IN (SELECT EMPNO FROM EMP GROUP BY EMPNO HAVING COUNT(EMPNO)>1) AND A.ROWID!=MIN (ROWID));

15. SELECT ENAME "EMPLOYEE",TO_CHAR(TRUNC(MONTHS_BETWEEN(SYSDATE,HIREDATE)/12))||' YEARS '|| TO_CHAR(TRUNC(MOD(MONTHS_BETWEEN (SYSDATE, HIREDATE),12)))||' MONTHS ' "LENGTH OF SERVICE" FROM EMP;

3 comments:

  1. in 1st query the condition should have been "A.ENAME= B.MGR'

    ReplyDelete
  2. Though most the queries work in SQL server, just want to put a note that the LPAD command doesn't exist in SQL server i guess.
    Ref :http://www.sqlservercurry.com/2011/10/sql-server-lpad-and-rpad-functions.html

    ReplyDelete