Oracle referential constraint?

You can use fewer columns, but the columns you do use have to have a UNIQUE constraint on them.

You can use fewer columns, but the columns you do use have to have a UNIQUE constraint on them. And, of course, if you can put a UNIQUE constraint on just part of the primary key, then you have to ask yourself a question: "Why does my primary key have more columns than it needs in the first place?

A FK isn't necessaraly the PK of the other table. It can be, but it doesn't have to. So you can use as FK as many columns as you need... From oracle: The foreign key in the child table will generally reference a primary key in the parent table.

Edit: the original question was about number of columns, not about using the incomplete PK as a FK. The FK must reference something that is unique in the other table. So, you'll have to use any column that have a UNIQUE constraint, or the PK of the other table (since the PK must also be unique.

For example, you select multiple columns from the table because each column, alone, is not unique, but the concatenation of multiple columns will be unique).

ORA-02270 says otherwise – Rnet Aug 1 at 12:21 ORA-02270 doesn't say otherwise considering your original question. It just says that the columns must be unique, and it doesn't relate to the number of columns. Your FK can have as many columns as you want (but limited to 32 in oracle), but all them must have the unique constraint.

– woliveirajr Aug 1 at 12:39.

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