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OUTER JOIN and EXISTS condition

Hello,

 Table Structure
The embedded image in this post has sample table structure and data related to my question.
Please refer to it.

Criteria
I want employee rec to be returned in the output if it satisfies any of the below 3 criterias:
If Employee's salary is > 0
or
If Employee exist in the EmployeeStatus table with EmpStatus as 'Active'
or
If Employee does not exist in the EmployeeStatus table


I should not get Employee = 4 in output as Kate's salary is 0, and although exist in the EmployeeStatus table, the EmpStatus is 'Inactive'                                                                  


Question:

I am trying to achieve this using EXISTS clause, but the problem is that when I use EXISTS, only Employee record that also exists in the EmployeeStatus gets returned.

Can you please show me how to achieve this using EXISTS approach, OUTER JOIN Approach, as well as anyother approach that would easily solve this problem.


Thanks!
0
sath350163
Asked:
sath350163
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2 Solutions
 
Guy Hengel [angelIII / a3]Billing EngineerCommented:
this approach should do the job:
select * 
from employee e
WHERE e.Salary > 0 
    OR EXISTS ( select NULL FROM EmployeeStatus es where es.employeeid = e.id and es.EmpStatus as 'Active' )
    OR NOT EXISTS ( select NULL FROM EmployeeStatus es where es.employeeid = e.id   )

Open in new window

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sath350163Author Commented:
Thank you so much for the response.


Can you also show me how to do this using CROSS APPLY (if its doable) and using OUTER JOIN?

Thanks!
0
 
sath350163Author Commented:
Would this approach work?

SELECT *
FROM Employee e LEFT OUTER JOIN EmployeeStatus es
ON e.Eno = es.Eno
AND (e.Salary > 0.00 OR es.EmpStatus = 'ACTIVE' OR es.EmpStatus IS NULL) 

Open in new window


When I execute this sql, I get the Eno = 4 also in the result, along with others.

But Eno = 4 has salary =0 and the EmpStatus is 'INACTIVE' in EmpStatus table,
So technically this Employee record should not be returned in the resultset.

What is the problem here?
Is sql server applying the condition for merging the records between the two tables, and not for filtering?

Thanks!
0
 
Guy Hengel [angelIII / a3]Billing EngineerCommented:
CROSS APPLY is not usable here ....


I would have said that your LEFT JOIN should work, but visible it does not ...
but I wonder why.
I have tested that my syntax does work ...

let me check if I find something on this ...
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Guy Hengel [angelIII / a3]Billing EngineerCommented:
this works again:
SELECT sq.*
FROM (Select e.*, es.EmpStatus
         FROM Employee e 
  LEFT OUTER JOIN EmployeeStatus es
      ON e.Eno = es.Eno
) sq
WHERE (sq.Salary > 0.00 OR sq.EmpStatus = 'ACTIVE' OR sq.EmpStatus IS NULL)  

Open in new window


visibly, the condition on EmpStatus here is not moved to the OUTER JOIN as in your code, but I couldn't see the actual technical reason.
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