To determine the combination of columns for a given column v in the join view table V, use the following procedure:
- Determine the base table Tj containing the column which corresponds to v.
- Determine the unique table sequence Til...Tik that contains Tj.
- Determine the last table Til in this sequence that has a 1:1 relationship with the key table.
- The columns of V, which correspond to the foreign key columns of Til of the referential CONSTRAINT definition between Til and Til+I that is relevant for V, are elements of the column combination.
- All columns of V which correspond to columns of the tables Til+l...Tik are elements of the column combination.
To update the column value of the column v in an