In any existing table, such as “college”, a unique constraint can be added using the “ ALTER TABLE” statement. Step 2: ADD UNIQUE CONSTRAINT in PostgreSQL The “ CREATE TABLE” message verifies that the “ college” table has been successfully created. Add columns such as std_id, teach_id, sport_date, and notes in this table: CREATE TABLE college( To drop unique constraints from a table, users must follow the syntax stated below: ALTER TABLE tbl_nameĭROP CONSTRAINT constraint_name UNIQUE (col_name) ĪLTER TABLE is a command in Postgres used to alter/modify a table, while “ DROP CONSTRAINT” is a clause that drops the existing unique constraint from the table.įirst, create a " college " table with the “ CREATE TABLE” statement. In the PostgreSQL database, the “ DROP CONSTRAINT” clause removes the rule or policy that is already set using the “ ADD CONSTRAINT” clause.
POSTGRES FOREIGN KEY CONSTRAINT HOW TO
How to DROP UNIQUE CONSTRAINT in PostgreSQL? Step 3: DROP UNIQUE CONSTRAINT in PostgreSQL.Step 2: ADD UNIQUE CONSTRAINT in PostgreSQL.How to DROP UNIQUE CONSTRAINT in PostgreSQL?.
The content that illustrates the demonstration is as follows: PostgreSQL's "DROP CONSTRAINT" clause with UNIQUE constraint is explained in this article. Using the DROP CONSTRAINT clause, users can drop any specific constraint, such as UNIQUE CONSTRAINT, FOREIGN KEY CONSTRAINT, CHECK CONSTRAINT, and so on. In PostgreSQL, the “ DROP CONSTRAINT” clause is used with the ALTER TABLE statement to drop any specific constraint from a table.
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