Subject Firebird SQL built-in function DATEADD with negative argument
Author Mike
When I use the DateAdd function in SQL it works OK with the following syntax:

DateAdd (MONTH, Delta, DateLast)

where Delta contains a number of months and DateLast contains a valid Date value.

However, if I want to decrement the result I use the following syntax:

DateAdd (MONTH, -Delta, DateLast)

and I get "Dynamic SQL error expression evaluation not supported".

I have tried -(Delta) ; -[Delta] ; [Delta]*-1 and so on but with no success.

What is the correct syntax for subtracting using DateAdd? Or, is there a bug?

Mike Watson
Datos Informatica.