Select specific columns from two tables - sql

Question

Suppose I have two tables tblEmployee and tblEmpSalary. I need to write a SQL statement to get a list of all employees, their name and salary, who receive the highest salary in each department.
Sample table data is here:

Answer 1

You could use ranking functions in this case:
WITH ranked AS (
SELECT
e.*,
s.monSalary,
rnk = RANK() OVER (PARTITION BY e.strDepartment ORDER BY s.monSalary DESC)
FROM tblEmplopyee e
INNER JOIN tblEmpSalary s ON e.intEmployeeID = s.intEmployeeID
)
SELECT
intEmploeeID,
strEmpName,
strDepartment,
monSalary
FROM ranked
WHERE rnk = 1
The RANK() function will do if you only need those who's got the topmost salary. With RANK(), the query may return more than employee per department if they have the same salary.
Alternatively, you can use DENSE_RANK() instead of RANK(), with the same effect, but DENSE_RANK() would also allow you to get employees with top n salaries. (You would be able to specify that in the WHERE condition like this:
WHERE rnk <= n
)
If, however, you need exactly one employee per department, even if there are several of them matching the requirement, use ROW_NUMBER() instead of RANK(). But then you'll probably need to add another criterion to the ORDER BY clause of the ranking function, e.g. like this:
... ORDER BY s.monSalary DESC, e.strEmpName ASC)
In fact, ROW_NUMBER() would simply make your query employee-oriented rather than salary-oriented. With ROW_NUMBER(), you would be able to have your query return top n most-paid employees, using the same condition as with DENSE_RANK():
WHERE rnk <= n
You can read more about ranking functions in SQL Server on MSDN:
Ranking Functions (Transact-SQL)

Answer 2

SELECT e.strEmpName, s.monSalary
FROM tblEmployee e
JOIN tblEmpSalary s ON e.intEmployeeID = s.intEmployeeID
WHERE e.strDepartment + '-' + CAST(s.monSalary AS varchar(20)) IN (
SELECT e2.strDepartment + '-' + CAST(MAX(s2.monSalary) AS varchar(20))
FROM tblEmployee e2
JOIN tblEmpSalary s2 ON e2.intEmployeeID = s2.intEmployeeID
GROUP BY e2.strDepartment)
Disclaimer: I can't test this query right now, so it could have some small detail wrong.

Answer 3

SELECT a.d, a.m, b.strEmpName
FROM (
SELECT strDepartment d, MAX(monSalary) m
FROM (
SELECT *
FROM tblEmployee e
LEFT JOIN tblEmpSalary s ON e.inEmployeeID = s.intEmployeeID
)
GROUP BY strDepartment
) a
LEFT JOIN (
SELECT *
FROM tblEmployee e
LEFT JOIN tblEmpSalary s ON e.inEmployeeID = s.intEmployeeID
) b ON a.d=b.strDepartment AND a.m=b.M

Answer 4

SELECT tblEmployee.strEmpName, max_salaries.strDepartment, max_salaries.salary
FROM (SELECT tblEmployee.strDepartment, MAX(monSalary)
FROM tblEmployee INNER JOIN tblEmpSalary
ON tblEmployee.intEmployeeID = tblEmpSalary.intEmployeeID
GROUP BY tblEmployee.strDepartment) max_salaries
INNER JOIN tblEmployee ON tblEmployee.strDepartment = max_salaries.strDepartment
INNER JOIN tblEmpSalary ON tblEmpSalary.monSalary = max_salaries.salary
AND tblEmpSalary.intEmployeeID = tblEmployee.intEmployeeID
In case of two or more employees with equal max salaries - this will return all of them for the specified department.