OK I think I get what you were saying. I was just too dense to get it. I think something like this should get you started.

CREATE PROC dbo.insert_into_child(@list_of_string_vals varchar(8000))

AS

BEGIN TRY

BEGIN TRAN

if exists

(

SELECT P.some_id

FROM dbo.DelimitedSplit8K(@list_of_string_vals, ',') C

LEFT JOIN dbo.parent P ON P.string_val = C.Item

where p.string_val is null

)

RAISERROR('Not all values are in parent table.', 11, 1) --Must have a severity of 11 or higher and less than 20 so we get to the catch block

INSERT INTO dbo.child(some_id_from_parent)

SELECT P.some_id

FROM dbo.DelimitedSplit8K(@list_of_string_vals, ',') C

LEFT JOIN dbo.parent P ON P.string_val = C.Item

COMMIT TRAN

END TRY

BEGIN CATCH

select 'Do something here'

rollback transaction

END CATCH