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Using the Result of a Function as the Criteria for a Query
 | Many people are unaware that the result of a function can serve as an expression in a query or as a parameter to a query. The query shown in Figure 11.39 evaluates the result of a function called Initials. The return value from the function is evaluated with criteria to determine whether the employee is included in the query result. The Initials function shown here (it's also in the basUtils module of CHAP11EX.MDB, found on the sample code CD-ROM) receives two strings and returns the first character of each string followed by a period: |
strLastName As String) As String
Initials = Left(strFirstName, 1) & "." & _
Left(strLastName, 1) & "."
End Function
Figure 11.39. A query that uses the result of a function as an expression.
| The return value from a function can also be used as the criteria for a query (see Figure 11.40). The query in the figure uses a function called HighlyPaid to determine which records appear in the query result. Here's what the HighlyPaid function looks like (it's also in the basUtils module of CHAP11EX.MDB, found on the sample code CD-ROM): |
Dim curHighRate As Currency
Select Case strTitle
Case "Sr. Programmer"
curHighRate = 60
Case "Systems Analyst"
curHighRate = 80
Case "Project Manager"
curHighRate = 100
Case Else
curHighRate = 50
End Select
HighlyPaid = curHighRate
End Function
Figure 11.40. A query that uses the result of a function as criteria.
The function receives the employee's title as a parameter. It then evaluates the title and returns a threshold value to the query that's used as the criterion for the query's Billing Rate column.
