Question

Simple structure table of employees

Employee      Manager
Joe Smith      Jon Smith
Jon Smith      Pete Stevens
Pete Stevens   NULL
Jared Scho     Pete Stevens
....

Im just trying to return some results but I want an indicator on whether the person is a manager or not so the result should be:

Employee       Manager      IsAManager
Joe Smith     Jon Smith         0
Jon Smith     Pete Stevens      1
Pete Stevens    NULL            1
Jared Scho    Pete Stevens      0

The result set is showing that Joe Smith and Jared Scho are not managers…

So If I had a simple SQL Query

SELECT
   Employee,
   Manager,
   As IsAManager   --tried to do a case statement here....
FROM
   Employee

I tried to do a case statement something to this effect:

SELECT CASE ISNULL(COUNT(*), 0) > 0 THEN 1 ELSE 0 END FROM Employee WHERE Manager = Employee

Not sure how to word it 🙂

Answer 1

Hopefully this is just a demo example not your real table structure.

SELECT Employee,
       Manager,
       CASE
         WHEN EXISTS(SELECT *
                     FROM   Employee e2
                     WHERE  e2.Manager = e1.Employee) THEN 1
         ELSE 0
       END As IsAManager
FROM   Employee e1  

For details of how SQL Server processes EXISTS Subqueries in CASE Expressions see this article.