Unique index/constraint on 2 columns in same table in Oracle

Question

I need to create a unique constraint/index on 2 columns in a table. One of these 2 columns can be null . My unique constraint/index needs to check if these 2 columns are not null then they cannot be duplicate.

Not sure how to tackle that, any starters?

Answer 1

You can use a primary key and function-based index for this. Here is an example:

create table t (
    id int primary key,
    x int,
    y int
);

create unique index t_x_y on t(x, y, (case when x is null or y is null then id end));

Here is a db<>fiddle.

Answer 2

Try using the NVL function on the column in the index/constraint.