>how to use 'IS NULL' operator ?
>i usually use isnull() in views with this command :
>iif(isnull(field0),x,y)

It's the same as NVL(x,y). In SQL Server it will be

ISNULL(x,y)

BTW, SQL Server T-SQL doesn't have IIF() either. The CASE() function can be used instead.