[PostgreSQL] Ensure uniqueness in Postgres

Let's say we have a bank. Our bank wants to give each account for each user a unique name, for instance, "Personal" or "Checking." How can we do sure each account have a unique name for each user?

ADD UNIQUE constraint when create a new table:

CREATE TABLE directors (  PRIMARYKEY,  VARCHAR(UNIQUE  notNULL    )

Change existing table, modify one field to is unique:

ALTER TABLE ADD CONSTRAINT UNIQUE (name)

So, if we trying to insert the duplicate rows it would report error:

INSERT  into VALUES (' Quintin Tarantino'), ('Quintin Tarantino');

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

ALTER TABLE ADD CONSTRAINT UNIQUE (title, Release-date)

[PostgreSQL] ensure uniqueness in Postgres