Function Running Many Times

Hello,

I see the following problem regarding a SQL function that returns a value.

We have the following query

SELECT c.Id_Customer, c.Name
FROM t_Customers c
WHERE c.Id_Status = fn_GetParameter('ID_Status.Active')

The idea is not hardcoding the status and other values on each query, and, since SQL Server does not support the definition of constants, we have a table with many parameters and we search them.

We defined the function "WITH SCHEMABINDING" and the SQL Server recognizes it as DETERMINISTIC, so I do not understand why it executes the function as many times as records in the t_Customers table, since every time it is executed it returns the same value.

We could define a variable, assign the value returned by this function to this variable and then use it on the SELECT, but this approach is useless if we use SQL instead of stored procedures (for example, in reports from reporting / BI tools).

Any explanation about why SQL chooses to execute the function many times, and any hint regarding how to make SQL Server execute only once the function will be very appreciated.

Thanks in advance,

Lisandro.