Field in table unique and null?

Question

PostgreSQL

I want to check the value for its uniqueness, while there are many entities in the table that have the value of the checked field null .
Can you please tell me what is in the box?
Doctrine, Symfony, PgSQL

Answer 1

I mean, do you want non-null values ​​to be unique? Make a unique index:

CREATE UNIQUE INDEX table_name_column_name_not_null ON table_name(column_name)
WHERE column_name IS NOT NULL;