how to fetch top distinct data in sqlserver - sql

Question

I have a table named employee_salary, with three columns: empsal_id, empsal_name and empsal_sal. The data is as follows:
empsal_id empsal_name empsal_sal
1 dilip 14000
2 santosh 20000
3 amit 32000
4 dilip 22000
5 amit 38000
6 santosh 25000
7 dilip 30000
The empsal_id is an Identity column with a Seed and an Increment of 1, and is the Primary Key. I want to return the name and current salary of each employee. Salary can decrease as well as increase, so current does not necessarily mean highest.
So I need the following output:
empname emp_sal
dilip 30000
amit 38000
santosh 25000
I am using Microsoft SQL Server, and I have to do this in a single query.

Answer 1

This query will return each employee, along with their highest salary:
SELECT
empsal_name, MAX(empsal_sal)
FROM
employee
GROUP BY
empsal_name
This query will return each employee, along with their current salary (i.e. the salary with the highest empsal_id:
SELECT
empsal_name, empsal_sal
FROM
employee e1
WHERE
empsal_id =
(SELECT MAX(empsal_id)
FROM employee e2
WHERE e1.empsal_name=e2.empsal_name)
Personally, I think you would be better off using an effective date column (e.g. empsal_effectivedate) to determine which record is the most current, so this query will return each employee, along with their current salary (i.e. the salary with the most recent empsal_effectivedate), assuming there is an empsal_effectivedate field:
SELECT
empsal_name, empsal_sal
FROM
employee e1
WHERE
empsal_effectivedate =
(SELECT MAX(empsal_effectivedate)
FROM employee e2
WHERE e1.empsal_name=e2.empsal_name)

Answer 2

Assuming there is also an ID in the table and also assuming that the larger this ID is the most recent the salary is for that employee you can do
SELECT DISTINCT
e.empname,
(SELECT TOP 1
emp_sal
FROM
employee s
WHERE
s.empname = e.empname
ORDER BY
recid DESC) AS emp_sal
FROM
employee e
(also assuming that empname is unique for an employee)
because of the many assumptions though : you should probably post all the columns of the table and what they mean ..

Answer 3

SELECT empname, MAX(emp_sal)
FROM employee
GROUP BY empname
UPDATED:
SELECT DISTINCT EmpA.empname,
EmpA.emp_sal
FROM Employee AS EmpA
INNER JOIN ( SELECT EmpName, MAX(recID) AS recid
FROM Employee
GROUP BY EmpName
) AS EmpB ON EmpA.recid = EmpB.recid;

Answer 4

You need a date field to determine the latest inserted row . In case if the table is linked to some other table which has date column in it .Then its pretty easy to fetch the current data .
For Example
Employee Table
{
EmpName varchar(30) PK,
EmpAddress varchar(255) ,
Company varchar(30),
CurrentTimeStamp Datetime
}
Salary Table
{
EmpName varchar(30) FK,
EmpSalary int
}
To get the Latest record use the CTE function
With LatestSal(EmpName ,EmpSalary)
AS
(
Select row_number() over (PARTITION BY b.[EmpName], order by CurrentTimestamp DESC) as seq
b.EmpName,b.EmpSalary
From Employee as a,
Salary as b
on a.[EmpName]=b.[EmpName]
)
Select EmpName,EmpSalary
from LatestSal
where seq=1