Example 2. A PL/pgSQL Trigger Procedure For Auditing This example trigger ensures that any insert, update or delete of a row in the emp table is recorded (i.e., audited) in the emp_audit table. The current time and user name are stamped into the row, together with the type of opera...
Example #4 – Drop trigger in PostgreSQL You can drop a trigger by dropping the “DROP TRIGGER” statement in PostgreSQL. Syntax DROP TRIGGER trigger_name on table_name; Example testing=# drop trigger trigger_test on the employee; Output: Conclusion You use the “CREATE TRIGGER” statement to...
The PostgreSQL CREATE TRIGGER is used to create a trigger in a PostgreSQL database. Create Trigger syntax CREATE TRIGGER name { BEFORE | AFTER | INSTEAD OF } ON table_name [FOR [EACH] {ROW | STATEMENT}] EXECUTE PROCEDURE function_name(arguments); Create Trigger example Step 1 – Create...
PostgreSQL ALTER TRIGGER example First, create a new table called employees: DROP TABLE IF EXISTS employees; CREATE TABLE employees( employee_id INT GENERATED ALWAYS AS IDENTITY, first_name VARCHAR(50) NOT NULL, last_name VARCHAR(50) NOT NULL, salary decimal(11,2) NOT NULL DEFAULT 0, PRIMARY...
PostgreSQL BEFORE DELETE trigger example We’ll use a BEFORE DELETE trigger to prevent applications from deleting a row in a table. First, create a table called products that stores the product data: CREATE TABLE products ( id SERIAL PRIMARY KEY, name VARCHAR(100) NOT NULL, price NUMERIC(10...
Where auditlogfunc() is a PostgreSQL procedure and has the following definition −CREATE OR REPLACE FUNCTION auditlogfunc() RETURNS TRIGGER AS $example_table$ BEGIN INSERT INTO AUDIT(EMP_ID, ENTRY_DATE) VALUES (new.ID, current_timestamp); RETURN NEW; END; $example_table$ LANGUAGE plpgsql;...
In our example, it was not difficult to avoid endless recursion with aWHEREcondition. It may not always be that easy. There is another way to stop recursion: the functionpg_trigger_depth(). This function is for use in trigger functions and returns the recursion level. We can use it as ...
PostgreSQL provides a very useful event-based trigger system to detect changes to data and automatically perform subsequent tasks. For example, triggers can be used to detect changes on one table and perform related changes on another table; a common form of this usage is a centralized audit ta...
PostgreSQL Trigger: Example BEFORE UPDATE We have a table student_marks with 10 columns and 4 rows. There are data only in STUDENT_ID and NAME columns. postgres=# SELECT * FROM STUDENT_MARKS; student_id | name | sub1 | sub2 | sub3 | sub4 | sub5 | total | per_marks | grade ...
Here, I describe what the return value of a PostgreSQL row level trigger function means and suggest a useful code simplification for such functions.