PostgreSQL – Disabling a Trigger
In PostgreSQL, there is no specific statement such as DISABLE TRIGGER for disabling an existing trigger. However, one can disable a trigger using the ALTER TABLE statement as follows:
Syntax:
ALTER TABLE table_name
DISABLE TRIGGER trigger_name | ALL
Let’s analyze the above syntax:
- First, you specify the name of the trigger, which you want to disable, after the DISABLE TRIGGER keywords.
- To disable all triggers associated with a table, you use ALL instead of a particular trigger name.
Example:
First, we create a staff table for demonstration with the below statement:
CREATE TABLE staff(
user_id serial PRIMARY KEY,
username VARCHAR (50) UNIQUE NOT NULL,
password VARCHAR (50) NOT NULL,
email VARCHAR (355) UNIQUE NOT NULL,
created_on TIMESTAMP NOT NULL,
last_login TIMESTAMP
);
Second, create a function that validates the username of a staff. The username of staff must not be null and its length must be at least 8.
CREATE FUNCTION check_staff_user()
RETURNS TRIGGER
AS $$
BEGIN
IF length(NEW.username) < 8 OR NEW.username IS NULL THEN
RAISE EXCEPTION 'The username cannot be less than 8 characters';
END IF;
IF NEW.NAME IS NULL THEN
RAISE EXCEPTION 'Username cannot be NULL';
END IF;
RETURN NEW;
END;
$$
LANGUAGE plpgsql;
Third, create a new trigger on the staff table to check the username of a staff. This trigger will fire whenever you insert or update a row in the staff table.
CREATE TRIGGER username_check
BEFORE INSERT OR UPDATE
ON staff
FOR EACH ROW
EXECUTE PROCEDURE check_staff_user();
Now we can disable the username_check triggered using the below statement:
ALTER TABLE staff
DISABLE TRIGGER username_check;
Output:
Last Updated :
28 Aug, 2020
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