how to retrieve highest and lowest salary from following table? - sql

Question

I have employee table
EMP_ID | F_NAME | L_NAME | SALARY | JOINING_DATE | DEPARTMENT
-----------------------------------------------------------------------------------
101 | John | Abraham | 100000 | 01-JAN-14 09.15.00.000000 AM | Banking
102 | Michel | Clarke | 800000 | | Insaurance
102 | Roy | Thomas | 70000 | 01-FEB-13 12.30.00.000000 PM | Banking
103 | Tom | Jose | 600000 | 03-FEB-14 01.30.00.000000 AM | Insaurance
105 | Jerry | Pinto | 650000 | 01-FEB-13 12.00.00.000000 PM | Services
106 | Philip | Mathew | 750000 | 01-JAN-13 02.00.00.000000 AM | Services
107 | TestName1 | 123 | 650000 | 01-JAN-13 12.05.00.000000 PM | Services
108 | TestName2 | Lname% | 600000 | 01-JAN-13 12.00.00.000000 PM | Insaurance
i want to find highest and lowest salary from above table in oracle sql.
if i do
select max(salary) from (select * from (select salary from employee) where rownum <2);
it returns MAX(SALARY) = 100000 where it should return 800000
If I do
select max(salary)
from (select * from (select salary from employee)
where rownum <3);
it returns MAX(SALARY) = 800000
If I do
select min(salary)
from (select * from(select salary from employee)
where rownum < 2);
it will return MIN(SALARY) = 100000 where it should return 70000.
What is wrong in this query?
what should be the correct query?

Answer 1

You don't need all these subqueries:
SELECT MAX(salary), MIN(salary)
FROM employee

Answer 2

SQL Fiddle
Oracle 11g R2 Schema Setup:
CREATE TABLE employee ( EMP_ID, F_NAME, L_NAME, SALARY, JOINING_DATE, DEPARTMENT ) AS
SELECT 101, 'John', 'Abraham', 100000, TIMESTAMP '2014-01-01 09:15:00', 'Banking' FROM DUAL
UNION ALL SELECT 102, 'Michel', 'Clarke', 800000, NULL, 'Insurance' FROM DUAL
UNION ALL SELECT 102, 'Roy', 'Thomas', 70000, TIMESTAMP '2013-02-01 12:30:00', 'Banking' FROM DUAL
UNION ALL SELECT 103, 'Tom', 'Jose', 600000, TIMESTAMP '2014-02-03 01:30:00', 'Insurance' FROM DUAL
UNION ALL SELECT 105, 'Jerry', 'Pinto', 650000, TIMESTAMP '2013-02-01 12:00:00', 'Services' FROM DUAL
UNION ALL SELECT 106, 'Philip', 'Mathew', 750000, TIMESTAMP '2013-01-01 02:00:00', 'Services' FROM DUAL
UNION ALL SELECT 107, 'TestName1', '123', 650000, TIMESTAMP '2013-01-01 12:05:00', 'Services' FROM DUAL
UNION ALL SELECT 108, 'TestName2', 'Lname%', 600000, TIMESTAMP '2013-01-01 12:00:00', 'Insurance' FROM DUAL;
Query 1 - To find the highest-n salaries:
SELECT *
FROM (
SELECT salary
FROM employee
ORDER BY salary DESC
)
WHERE rownum <= 3 -- replace with the number of salaries you want to retrieve.
Results:
| SALARY |
|--------|
| 800000 |
| 750000 |
| 650000 |
Query 2 - To find the lowest-n salaries:
SELECT *
FROM (
SELECT salary
FROM employee
ORDER BY salary ASC
)
WHERE rownum <= 3 -- replace with the number of salaries you want to retrieve.
Results:
| SALARY |
|--------|
| 70000 |
| 100000 |
| 600000 |

Answer 3

For each row returned by a query, the ROWNUM pseudocolumn returns a number indicating the order in which Oracle selects the row from a table or set of joined rows. The first row selected has a ROWNUM of 1, the second has 2, and so on.
So in your case :
select max(salary) from (select * from (select salary from employee) where rownum <2);
This query will return
101 John Abraham 100000 01-JAN-14 09.15.00.000000 AM Banking
only this row as output... and hence the max value will be 100000 only.
select max(salary) from (select * from (select salary from employee) where rownum <3);
This query will tak first 2 rows from your table, i.e.,
101 John Abraham 100000 01-JAN-14 09.15.00.000000 AM Banking
102 Michel Clarke 800000 Insaurance
and hence the max salary will be 800000.
Similarly,
select min(salary)from (select * from(select salary from employee)where rownum<2);
will only select 1st row
select min(salary)from (select * from(select salary from employee)where rownum<2);
so min salary will be 100000.
P.S. : You could simply write your queries like this :
select max(salary) from employee where rownum<[n];
where n will be ROWNUM to which you want to limit the number of rows returned by your query

Answer 4

Try it:
select *
from (
select T.*, rownum RRN
from (
select salary
from employee
order by salary desc) T)
where RRN < 3

Answer 5

so you want the 2nd highest and 2nd lowest salary? Check this out
select max(salary), min(salary) from employee
where salary < (select max(salary) from employee)
and salary > (select min(salary) from employee)
;

Answer 6

1) For lowest salary.
select * from (
select empno,job,ename,sal
from emp order by sal)
where rownum=1;
2) For Highest salary.
select * from (
select empno,job,ename,sal
from emp order by sal desc)
where rownum=1;

Answer 7

i don't know why you make complicated queries you can simply write this and get the same result:
select salary
from employees
where rownum <=3
order by salary desc;

Answer 8

you can solve your problem with following queries:
Highest salary:
Select * from Employee(Select salary from Employee ORDER BY salary DISC) where rownum=1;
Lowest salary:
Select * from Employee(Select salary from Employee ORDER BY salary) where rownum=1;
Second highest salary:
Select MAX(Salary) from Employee
Where Salary < (Select MAX(Salary) from employee);
Second Lowest salary :
Select MIN(Salary) from Employee
Where Salary > (Select MIN(Salary) from employee);