asked on

check constraint

I have two tables:

tbl_ProjectEmployee
PK-QualficiationID (Part of composite PK)

tbl_ProjectQualification
PK-QualificationID (Part of Composite PK)
Qualification Count

I want to place a check constraint on tbl_ProjectEmployee that does not exceed the QualificationCount in the second table.

Here's my code but I'm stuck:

ALTER TABLE dbo.tbl_ProjectEmployee ADD CONSTRAINT CK_QualificationID
CHECK (QualificationID <= (Select QualificationCount from dbo.tbl_ProjectQualification pq
where pk.QualificationID = QualificationID)

Error:

Msg 1046, Level 15, State 1, Line 2
Subqueries are not allowed in this context. Only scalar expressions are allowed.

Guy Hengel [angelIII / a3]

as the error indicates: you cannot do that with a subquery.

however, as from sql 2008, you can workaround by creating a function:
http://sqlblogcasts.com/blogs/tonyrogerson/archive/2008/02/07/using-a-udf-in-a-check-constraint-to-check-validity-of-history-windows-start-end-date-windows.aspx

Glen_D

ASKER

I thought a function may work better but stuck with this as well:

Create Function (fn_QualificationCount) (@qualificationID int)
as
Begin
Declare @pe int
Declare @q1 int
Declare @q2 int
Declare @count int
set @pe = (select QualificationID from dbo.tbl_ProjectEmployee)
set @q1 = (select QualificationCount from dbo.tbl_ProjectQualification
                  where QualificationID = @pe)
set @q2 = (select COUNT (QualificationID) from dbo.tbl_ProjectEmployee
                  where QualificationID = @pe)
set @count = (@q1 - @q2)

If @count <= @p1
then

Else

ASKER CERTIFIED SOLUTION

Guy Hengel [angelIII / a3]

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

Glen_D

ASKER

Angel...that was great except for a minor syntax error in the function:

Create Function dbo.fn_QualificationCount (@qualificationID int) returns int
as
Begin
return (select QualificationCount
from dbo.tbl_ProjectQualification
where QualificationID = @qualificationID
)
end

Everything wa sgreat...

Thanks

Glen

Guy Hengel [angelIII / a3]

glad I could help

sorry for the type, I am working in so many programming languages that sometimes I mess up ...

CHeers