sql query returning unexpected results on NOT IN
I have query that should return results, but doesn't.
First I have an employeeUnitJob table. It has no records in it for this employee:
The query is:
It returns no rows as expected.
I want to do a query that returns the employees who have no rows in the employeeunitJobtype table, so I do this query, and just for testing I add the employeeID of this one employee that I know doesn't have a row in the table:
But this ALSO returns no rows. as though everyone has a unit/job and this person does not!
Is there something I am doing wrong? Why is the above query NOT returning any rows? it should return this employee?
thanks!
First I have an employeeUnitJob table. It has no records in it for this employee:
The query is:
select * from EmployeeUnitJobType where EmployeeId = 159795It returns no rows as expected.
I want to do a query that returns the employees who have no rows in the employeeunitJobtype table, so I do this query, and just for testing I add the employeeID of this one employee that I know doesn't have a row in the table:
SELECT *
FROM Employee
WHERE
Employee.EmployeeId NOT IN (select EmployeeId from EmployeeUnitJobType)
AND EmployeeId = 159795But this ALSO returns no rows. as though everyone has a unit/job and this person does not!
Is there something I am doing wrong? Why is the above query NOT returning any rows? it should return this employee?
thanks!
Scott Pletcher
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Both work, but I do prefer the second, although it might not be as politically correct. We have a lot of units and jobs per employee and I'm thinking the second might return multiple rows and I only want one row returned.
thanks!
thanks!
"NOT IN" is roughly equivalent to a "NOT EXISTS", both of which take advantage of the anti semi join. SQL won't usually convert a left join and check for NULL into an anti join, and, if not, it's usually less efficient.
Btw, DISTINCT performs better than GROUPing when all you need to do is get distinct values, so if you do decide to use that approach, code it like this instead:
LEFT JOIN (SELECT DISTINCT EmployeeId from EmployeeUnitJobType) t
Btw, DISTINCT performs better than GROUPing when all you need to do is get distinct values, so if you do decide to use that approach, code it like this instead:
LEFT JOIN (SELECT DISTINCT EmployeeId from EmployeeUnitJobType) t
ASKER
thanks scott!