Oracle SQL sample database - sql

Question

I'm trying to learn Oracle SQL by database Supplied by it.
I found somewhere tasks to be done.
Database structure is supplied by Oracle:
CREATE TABLE EMP
(EMPNO NUMERIC(4) NOT NULL,
ENAME VARCHAR(10),
JOB VARCHAR(9),
MGR NUMERIC(4),
HIREDATE DATETIME,
SAL NUMERIC(7, 2),
COMM NUMERIC(7, 2),
DEPTNO NUMERIC(2))
INSERT INTO EMP VALUES
(7369, 'SMITH', 'CLERK', 7902, '17-DEC-1980', 800, NULL, 20)
INSERT INTO EMP VALUES
(7499, 'ALLEN', 'SALESMAN', 7698, '20-FEB-1981', 1600, 300, 30)
INSERT INTO EMP VALUES
(7521, 'WARD', 'SALESMAN', 7698, '22-FEB-1981', 1250, 500, 30)
INSERT INTO EMP VALUES
(7566, 'JONES', 'MANAGER', 7839, '2-APR-1981', 2975, NULL, 20)
INSERT INTO EMP VALUES
(7654, 'MARTIN', 'SALESMAN', 7698, '28-SEP-1981', 1250, 1400, 30)
INSERT INTO EMP VALUES
(7698, 'BLAKE', 'MANAGER', 7839, '1-MAY-1981', 2850, NULL, 30)
INSERT INTO EMP VALUES
(7782, 'CLARK', 'MANAGER', 7839, '9-JUN-1981', 2450, NULL, 10)
INSERT INTO EMP VALUES
(7788, 'SCOTT', 'ANALYST', 7566, '09-DEC-1982', 3000, NULL, 20)
INSERT INTO EMP VALUES
(7839, 'KING', 'PRESIDENT', NULL, '17-NOV-1981', 5000, NULL, 10)
INSERT INTO EMP VALUES
(7844, 'TURNER', 'SALESMAN', 7698, '8-SEP-1981', 1500, 0, 30)
INSERT INTO EMP VALUES
(7876, 'ADAMS', 'CLERK', 7788, '12-JAN-1983', 1100, NULL, 20)
INSERT INTO EMP VALUES
(7900, 'JAMES', 'CLERK', 7698, '3-DEC-1981', 950, NULL, 30)
INSERT INTO EMP VALUES
(7902, 'FORD', 'ANALYST', 7566, '3-DEC-1981', 3000, NULL, 20)
INSERT INTO EMP VALUES
(7934, 'MILLER', 'CLERK', 7782, '23-JAN-1982', 1300, NULL, 10)
CREATE TABLE DEPT
(DEPTNO NUMERIC(2),
DNAME VARCHAR(14),
LOC VARCHAR(13) )
INSERT INTO DEPT VALUES (10, 'ACCOUNTING', 'NEW YORK')
INSERT INTO DEPT VALUES (20, 'RESEARCH', 'DALLAS')
INSERT INTO DEPT VALUES (30, 'SALES', 'CHICAGO')
INSERT INTO DEPT VALUES (40, 'OPERATIONS', 'BOSTON')
CREATE TABLE BONUS
(ENAME VARCHAR(10),
JOB VARCHAR(9),
SAL NUMERIC,
COMM NUMERIC)
CREATE TABLE SALGRADE
(GRADE NUMERIC,
LOSAL NUMERIC,
HISAL NUMERIC)
INSERT INTO SALGRADE VALUES (1, 700, 1200)
INSERT INTO SALGRADE VALUES (2, 1201, 1400)
INSERT INTO SALGRADE VALUES (3, 1401, 2000)
INSERT INTO SALGRADE VALUES (4, 2001, 3000)
INSERT INTO SALGRADE VALUES (5, 3001, 9999)
Now I would like to Select employees that earn most in their department and salgrade.
I wrote something like this one:
select ename, salgrade.grade, dept.dname from emp, salgrade, dept
WHERE emp.sal BETWEEN salgrade.losal AND salgrade.hisal
AND emp.deptno = dept.deptno group by salgrade.grade, dept.dname, emp.ename
But it's not working properly.
The output is:
ENAME GRADE DNAME
SMITH 1 RESEARCH
BLAKE 4 SALES
FORD 4 RESEARCH
KING 5 ACCOUNTING
SCOTT 4 RESEARCH
MILLER 2 ACCOUNTING
TURNER 3 SALES
WARD 2 SALES
MARTIN 2 SALES
ADAMS 1 RESEARCH
JONES 4 RESEARCH
JAMES 1 SALES
CLARK 4 ACCOUNTING
ALLEN 3 SALES
Note rows:
WARD 2 SALES
MARTIN 2 SALES
2 people from same department and salgrade.
Could you point me my mistakes?

Answer 1

You are not filtering your query this is why you have all the employees displayed.
This would filter the employees that earn less than the max for their dept/grade:
SELECT ename, salgrade.grade, dept.dname
FROM emp, salgrade, dept
WHERE emp.sal BETWEEN salgrade.losal AND salgrade.hisal
AND emp.deptno = dept.deptno
AND emp.sal = (SELECT MAX(sal)
FROM emp emp_in, salgrade grade_in
WHERE emp_in.sal BETWEEN grade_in.losal AND grande_in.hisal
AND emp_in.deptno = emp.deptno
AND grade_in.losal = salgrade.losal)
You will still find duplicates because for instance, two people in sales earn the max salary for grade 2 (both Martin and Ward earn 1250). Either this is acceptable or you need some other criteria to only select one of them.
You can use the row_number analytic function to ensure that only one row is returned by grade/dept (note that Oracle will select arbitrarily one row when there are duplicates) :
SELECT * FROM (
SELECT ename, salgrade.grade, dept.dname,
row_number() OVER (PARTITION BY dept.deptno, salgrade.grade
ORDER BY emp.sal DESC) rnk
FROM emp, salgrade, dept
WHERE emp.sal BETWEEN salgrade.losal AND salgrade.hisal
AND emp.deptno = dept.deptno
) WHERE rnk = 1;
ENAME GRADE DNAME RNK
---------- ------ -------------- ---
MILLER 2 ACCOUNTING 1
CLARK 4 ACCOUNTING 1
KING 5 ACCOUNTING 1
ADAMS 1 RESEARCH 1
FORD 4 RESEARCH 1
JAMES 1 SALES 1
MARTIN 2 SALES 1
ALLEN 3 SALES 1
BLAKE 4 SALES 1

Answer 2

With your `select:
select ename, salgrade.grade, dept.dname from emp, salgrade, dept
WHERE emp.sal BETWEEN salgrade.losal AND salgrade.hisal
AND emp.deptno = dept.deptno group by salgrade.grade, dept.dname, emp.ename
when you group by salgrade.grade, dept.dname, emp.ename the results will be grouped into those three values. You also put the results BETWEEN salgrade.losal AND salgrade.hisal so it will give all employees that have the salary in that interval. It's not restricting anything to the greater one got it? And that's why you have WARD 2 SALES and MARTIN 2 SALES.

Answer 3

You are grouping by employee name, as well as department and salary grade. That means you will return a row for every combination of employee name, department and salary grade in your dataset.
To ensure that you only return one row per department and salary grade, you will need to remove the employee name from the group by clause. This will enable you to find the maximum salary per grade and department, but not which employees have that salary - to do that, you need to join the results back to the employee table again, like so:
select e.ename, s.grade, d.dname, e.salary
from (select max(emp.salary) max_salary,
salgrade.grade,
emp.deptno
from emp, salgrade
WHERE emp.sal BETWEEN salgrade.losal AND salgrade.hisal
group by salgrade.grade, dept.dname) s
join emp e on e.salary = s.max_salary
join dept d on e.deptno = d.deptno
Note that if multiple employees in the same department are earning the same maximum salary within their grade, then both employees will be returned - this should happen with FORD and SCOTT in RESEARCH.

Answer 4

SELECT SUB2.ENAME , SUB2.DNAME , S.GRADE ,SUB2.SAL
FROM SALGRADE S,
(SELECT E.ENAME,E.SAL,D.DNAME
FROM EMP E, DEPT D,
(SELECT DEPTNO, MAX(SAL) AS "MAX"
FROM EMP
GROUP BY DEPTNO) SUB1
WHERE E.SAL=SUB1.MAX
AND E.DEPTNO=D.DEPTNO) SUB2
WHERE SUB2.SAL BETWEEN S.LOSAL AND S.HISAL

Answer 5

Screen Shot ////// Try this out
SELECT E.EMPNO, E.ENAME, E.JOB, D.DNAME, E.SAL, E.DEPTNO, S.GRADE
FROM EMP E, SALGRADE S, DEPT D
WHERE E.SAL IN (SELECT MAX(SAL) FROM EMP GROUP BY DEPTNO)
AND E.SAL BETWEEN S.LOSAL AND S.HISAL
AND E.DEPTNO = D.DEPTNO
ORDER BY E.SAL DESC

Answer 6

When I created this I used this format to make it easier to read and modify it is for an Oracle format
CREATE TABLE EMP
(EMP_NO NUMBER(4) NOT NULL PRIMARY KEY,
E_NAME VARCHAR2(10),
JOB VARCHAR2(9),
MGR NUMBER(4),
HIRE_DATE DATE,
SAL DECIMAL(7, 2),
COMM DECIMAL(7, 2),
DEPT_NO NUMBER(2));
SELECT *
FROM EMP
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7369, 'SMITH', 'CLERK', 7902, '17-DEC-1980', 800, NULL, 20);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7499, 'ALLEN', 'SALESMAN', 7698, '20-FEB-1981', 1600, 300, 30);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7521, 'WARD', 'SALESMAN', 7698, '22-FEB-1981', 1250, 500, 30);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7566, 'JONES', 'MANAGER', 7839, '02-APR-1981', 2975, NULL, 20);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7654, 'MARTIN', 'SALESMAN', 7698, '28-SEP-1981', 1250, 1400, 30);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7698, 'BLAKE', 'MANAGER', 7839, '01-MAY-1981', 2850, NULL, 30);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7782, 'CLARK', 'MANAGER', 7839, '09-JUN-1981', 2450, NULL, 10);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7788, 'SCOTT', 'ANALYST', 7566, '09-DEC-1982', 3000, NULL, 20);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7839, 'KING', 'PRESIDENT', NULL, '17-NOV-1981', 5000, NULL, 10);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7844, 'TURNER', 'SALESMAN', 7698, '08-SEP-1981', 1500, 0, 30);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7876, 'ADAMS', 'CLERK', 7788, '12-JAN-1983', 1100, NULL, 20);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7900, 'JAMES', 'CLERK', 7698, '03-DEC-1981', 950, NULL, 30);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7902, 'FORD', 'ANALYST', 7566, '03-DEC-1981', 3000, NULL, 20);
INSERT INTO EMP
(EMP_NO, E_NAME, JOB, MGR, HIRE_DATE, SAL, COMM, DEPT_NO)
VALUES
(7934, 'MILLER', 'CLERK', 7782, '23-JAN-1982', 1300, NULL, 10);
CREATE TABLE DEPT
(DEPT_NO NUMERIC(2),
D_NAME VARCHAR(14),
LOC VARCHAR(13) );
INSERT INTO DEPT
(DEPT_NO, D_NAME, LOC)
VALUES
(10, 'ACCOUNTING', 'NEW YORK');
INSERT INTO DEPT
(DEPT_NO, D_NAME, LOC)
VALUES
(20, 'RESEARCH', 'DALLAS');
INSERT INTO DEPT
(DEPT_NO, D_NAME, LOC)
VALUES
(30, 'SALES', 'CHICAGO');
INSERT INTO DEPT
(DEPT_NO, D_NAME, LOC)
VALUES
(40, 'OPERATIONS', 'BOSTON');
CREATE TABLE BONUS
(E_NAME VARCHAR(10),
JOB VARCHAR(9),
SAL NUMERIC,
COMM NUMERIC);
CREATE TABLE SAL_GRADE
(GRADE NUMERIC,
LO_SAL NUMERIC,
HI_SAL NUMERIC);
INSERT INTO SAL_GRADE
(GRADE, LO_SAL, HI_SAL)
VALUES
(1, 700, 1200);
INSERT INTO SAL_GRADE
(GRADE, LO_SAL, HI_SAL)
VALUES
(2, 1201, 1400);
INSERT INTO SAL_GRADE
(GRADE, LO_SAL, HI_SAL)
VALUES
(3, 1401, 2000);
INSERT INTO SAL_GRADE
(GRADE, LO_SAL, HI_SAL)
VALUES
(4, 2001, 3000);
INSERT INTO SAL_GRADE
(GRADE, LO_SAL, HI_SAL)
VALUES
(5, 3001, 9999);