Reference Table

Hi,

I am creating a purchase header and item table(With same fields as in the standard table) in SE11. But when iam creating the Purchase item, it is giving error that

ZPURI-MENGE (specify reference table AND reference field)

ZPURI-NETPR (specify reference table AND reference field)

ZPURI-NETWR (specify reference table AND reference field)

Table ZPURI must be created in the database

Check on table ZPURI resulted in errors.

Why Iam getting the error when iam creating the purchase item table only?