[PostgreSQL] Ensure Uniqueness in Postgres

Change existing table, modify one field to be unique:

ALTER TABLE directors ADD CONSTRAINT directors_name_unique UNIQUE(name)

So now if we trying to insert the duplicate rows it will report error:

INSERT INTO directors (name) VALUES (‘Quintin Tarantino‘), (‘Quintin Tarantino‘) ;

Sometime, the unique constraint can be a combination of mulit fields:

ALTER TABLE movies ADD CONSTRAINT unique_title_and_release UNIQUE(title, release-date)

[PostgreSQL] Ensure Uniqueness in Postgres

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