#POSTGRES DROP FOREIGN KEY CONSTRAINT HOW TO#

To drop a foreign key constraint from a table, use the ALTER TABLE with the DROP CONSTRAINT clause: ALTER TABLE orders_details The output snippet shows that the foreign key constraint has been added to the orders_details table successfully. To do that, let’s run the below statement: ALTER TABLE orders_detailsįOREIGN KEY (customer_id) REFERENCES customers_info (c_id) Suppose we want to refer the “ customer_id” column from the “ orders_details” table to the “ c_id” column of the “ order_details” table. To explain the concept of foreign key constraint, we will use the “staff_info” and “employee_info” tables, whose details are shown below: SELECT * FROM customers_info SELECT * FROM orders_details

#POSTGRES DROP FOREIGN KEY CONSTRAINT HOW TO#

In this section, we will learn how to add or drop a FOREIGN KEY CONSTRAINT in Postgres Using ALTER TABLE command. How to Drop a FOREIGN KEY CONSTRAINT in Postgres?Ī FOREIGN KEY is a column that points to the PRIMARY KEY of some other Postgres table. The output clarifies that the primary key constraint has been removed successfully. Let’s verify the constraint deletion via the below command: SELECT * FROM staff_bio In this coding example, we dropped a primary key constraint named st_id_pk from the staff_bio table: The DROP CONSTRAINT clause can be used in conjunction with ALTER TABLE to drop a primary key constraint from a Postgres table. This way, you can add a primary key to any table’s column. Let’s validate the table’s structure via the following command: SELECT * FROM staff_bio The “ALTER TABLE” message in the output window proves that the “staff_bio” table has been modified successfully. The “st_id” represents a primary key column. The “st_id_pk” represents the name of the primary key. The “staff_bio” is a table to be altered. This section will teach you how to add or drop a PRIMARY KEY CONSTRAINT in Postgres Using ALTER TABLE command.įirstly, let’s add a primary key constraint on the “st_id” column using ALTER TABLE command and ADD CONSTRAINT clause: ALTER TABLE staff_bio In Postgres, Primary keys are used to identify a table’s record uniquely. How to Drop a PRIMARY KEY CONSTRAINT in Postgres? The table name staff_bio has been created with four columns: st_id, st_name, st_department, and st_age. Afterward, we will add and drop a specific constraint according to the requirement. How to Remove/Drop a NOT NULL CONSTRAINT From a Postgres Table?įirstly, we will create a sample table with some columns without any constraints.How to Drop a CHECK CONSTRAINT in Postgres?.How to Drop a UNIQUE CONSTRAINT in Postgres?.How to Drop a FOREIGN KEY CONSTRAINT in Postgres?.How to Drop a PRIMARY KEY CONSTRAINT in Postgres?.

The following content will be covered in this section regarding adding or dropping a CONSTRAINT in PostgreSQL: To drop any particular constraint from a Postgres table, users must execute the DROP CONSTRAINT with the ALTER TABLE command. This blog post will explain how to drop a constraint in PostgreSQL through Practical examples. For instance, PRIMARY KEY CONSTRAINT, UNIQUE CONSTRAINT, FOREIGN KEY CONSTRAINT, CHECK CONSTRAINT, or NOT NULL CONSTRAINT. If the account number exists, proceed with the insertion.PostgreSQL offers a “ DROP CONSTRAINT” clause that allows us to drop any constraint from an existing table. RAISE EXCEPTION 'account_number % does not exist in bank_account', NEW.account_number IF NOT EXISTS (SELECT 1 FROM bank_account WHERE account_number = NEW.account_number) THEN

If the account number doesn't exist in bank_account, raise an exception. CREATE OR REPLACE FUNCTION check_account_number_exists() Should this also not meet your wishes / requirements, you must somehow create the data integrity itself. What you could do, however, would be to define a function that triggers the insert and thus ensures that at least when inserting into the history, the bank account exists. Which is perfectly fine for historical data and does not speak against the normalization itself. So the solution would be to omit the foreign key. Since you don't want either action, nor do you want to ensure that the intrigue of the two tables remains, you don't want to use any property of the foreign key definition at this point. Alternatively you could set the foreign key to null. By default, PostgreSQL will throw an error if the foreign key is defined and a key element is to be deleted. Foreign keys always have the task of ensuring the integrity between 2 tables.

Postgres drop foreign key constraint