Question

I want to alter a view as follows:

ALTER VIEW [dbo].[ViewOne] as  
SELECT columnOne,  -- not null  
       columnTwo, --not null
      (convert(decimal(2,0), columnOne)) as columnThree -- I want this not to be NULL
FROM DBOne.TableOne

Since columnOne is “not null” I want to force columnThree to be “not null” also.
Is is possible, impossible, implicit, useless or could cause serious problems since columnOne is char(2) populated with algarisms only.

I simply would like to know the syntax

Answer 1

ColumnThree will never be null if the source of the Cast is itself never null. However, that does not mean you will not get an exception if ColumnOne cannot be cast to decimal(2,0) and you will not know whether you will get an exception until you query against the view. You should consider adding an additional check to determine whether the cast will fail and help mitigate the possibility of a cast error:

Alter View dbo.ViewOne
As
Select ColumnOne, ColumnTwo
    , Case
        When IsNumeric( ColumnOne ) = 0 Then 0
        Else Cast( ColumnOne As decimal(2,0) )
        End As ColumnThree