We will create two tables and will apply a foreign key. We will understand this with the help of a simple example. Lastly, we will state the delete and update actions in the ON DELETE and ON UPDATE clauses. Now, we will explain the parent table and parent key columns referenced by the foreign key columns in the REFERENCES clause. Then, we will describe one or more foreign key columns in parentheses after the FOREIGN KEY keywords. The CONSTRAINT clause is optional and if we ignore it, PostgreSQL will assign an auto-generated name. In the above syntax firstly we have specified the name for the foreign key constraint after the CONSTRAINT keyword. REFERENCES parent_table(parent_key_columns) The below explains a foreign key constraint syntax. In PostgreSQL, the foreign key’s values are parallel to the actual values of the primary key in the other table which is called a Referential integrity Constraint. The foreign key is basically known as the referencing key, and it matches the primary key field from another table, which signifies that the foreign key field in one table refers to another table’s primary key field. It has value in one column or group of columns displayed in the same column or a combination of columns in another table. Postgresql add foreign key on delete cascadeĪ group of columns with its values dependent on the primary key benefits from another table is known as the Foreign key in Postgresql.Postgresql add foreign key constraint to existing table.Postgresql add foreign key constraint to existing column.Postgresql add foreign key if not exists.
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