>>>I now tried the original suggestion.
>>
>>Did your original suggestion work?
>
>For me it is a little backward, but that works:
>

>IF NOT EXISTS(SELECT column_name
>                     FROM INFORMATION_SCHEMA.COLUMNS
>              WHERE TABLE_NAME = N'Volunteers' and COLUMN_NAME = N'IsActive')
>   BEGIN
>        alter table Volunteers add IsActive bit NULL CONSTRAINT [DF_Volunteers_IsActive] DEFAULT (1)
>        EXEC sp_executesql N'UPDATE Volunteers SET IsActive = 1'
>   END
> SELECT * FROM Volunteers
>

And if you switch (first line with EXEC) and second regular UPDATE, does it still work?