When Exists (
                    Select 1
                    From TableB
                    Where SomeField = 1
                        And ...
                    ) Then TableA.Field2
        Else Null
        End As Field2
    , Case
        When Exists (
                    Select 1
                    From TableB
                    Where SomeField = 1
                        And ...
                    ) Then TableA.Field3
        Else Null