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# PostgreSQL ALTER TRIGGER Statement

**Summary**: in this tutorial, you will learn how to use the PostgreSQL `ALTER TRIGGER` statement to rename a trigger.

## Introduction to PostgreSQL ALTER TRIGGER statement

The `ALTER TRIGGER` statement allows you to rename a trigger. The following shows the syntax of the `ALTER TRIGGER` statement:

```sql
ALTER TRIGGER trigger_name
ON table_name
RENAME TO new_trigger_name;
```

In this syntax:

- First, specify the name of the trigger you want to rename after the `ALTER TRIGGER` keywords.
- Second, provide the name of the table associated with the trigger after the `ON` keyword.
- Third, specify the new name of the trigger after the `RENAME TO` keyword.

To execute the `ALTER TRIGGER` statement, you must be the owner of the table to which the trigger belongs.

## PostgreSQL ALTER TRIGGER example

First, [create a new table](../postgresql-tutorial/postgresql-create-table) called `employees`:

```sql
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 KEY(employee_id)
);
```

Second, [create a function](../postgresql-plpgsql/postgresql-create-function) that raises an exception if the new salary is greater than the old one 100%:

```plsql
CREATE OR REPLACE FUNCTION check_salary()
  RETURNS TRIGGER
  LANGUAGE PLPGSQL
  AS
$$
BEGIN
	IF (NEW.salary - OLD.salary) / OLD.salary >= 1 THEN
		RAISE 'The salary increment cannot that high.';
	END IF;

	RETURN NEW;
END;
$$
```

Third, create a before-update trigger that executes the `check_salary()` function before updating the salary:

```sql
CREATE TRIGGER before_update_salary
  BEFORE UPDATE
  ON employees
  FOR EACH ROW
  EXECUTE PROCEDURE check_salary();
```

Fourth, [insert a new row](../postgresql-tutorial/postgresql-insert) into the `employees` table:

```sql
INSERT INTO employees(first_name, last_name, salary)
VALUES('John','Doe',100000);
```

Fifth, update the salary of the employee id 1:

```sql
UPDATE employees
SET salary = 200000
WHERE employee_id = 1;
```

The trigger was fired and issued the following error:

```
ERROR:  The salary increment cannot that high.
CONTEXT:  PL/pgSQL function check_salary() line 4 at RAISE
SQL state: P0001
```

It works as expected.

Finally, use the `ALTER TRIGGER` statement to rename the `before_update_salary` trigger to `salary_before_update`:

```sql
ALTER TRIGGER before_update_salary
ON employees
RENAME TO salary_before_update;
```

If you use psql tool, you can view all triggers associated with a table using the `\dS` command:

```
\dS employees
```

Notice that the letter `S` is uppercase.

![](https://neon.com/postgresqltutorial/PostgreSQL-ALTER-TRIGGER-example.png)

## Replacing triggers

PostgreSQL versions 14 and later support the `OR REPLACE` statement that allows you to modify the trigger definition like the function that will be executed when the trigger is fired.

The following example illustrates how to change the `check_salary` function of the `salary_before_update` trigger to `validate_salary`:

```sql
CREATE OR REPLACE TRIGGER salary_before_update
  BEFORE UPDATE
  ON employees
  FOR EACH ROW
  EXECUTE PROCEDURE validate_salary();
```

In versions prior to 14, the `OR REPLACE` statement was not supported, and to do so, you would have to use the `DROP TRIGGER` and `CREATE TRIGGER` statements. You can also wrap these statements within a [transaction](../postgresql-tutorial/postgresql-transaction) to guarantee the trigger with the old function is dropped in favor of the one with the new function.

```sql
BEGIN;

DROP TRIGGER IF EXISTS salary_before_update
ON employees;

CREATE TRIGGER salary_before_update
  BEFORE UPDATE
  ON employees
  FOR EACH ROW
  EXECUTE PROCEDURE validate_salary();

COMMIT;
```

## Summary

- Use the `ALTER TRIGGER` statement to rename a trigger.
- Use the `CREATE OR REPLACE TRIGGER` statement in new versions of PostgreSQL to replace a trigger with a new one or the pair of the `DROP TRIGGER` and `CREATE TRIGGER` statements in older versions.

---

## Related docs (PostgreSQL Triggers)

- [Introduction](https://neon.com/postgresql/postgresql-triggers/introduction-postgresql-trigger)
- [CREATE TRIGGER](https://neon.com/postgresql/postgresql-triggers/creating-first-trigger-postgresql)
- [DROP TRIGGER](https://neon.com/postgresql/postgresql-triggers/postgresql-drop-trigger)
- [AFTER INSERT Trigger](https://neon.com/postgresql/postgresql-triggers/postgresql-after-insert-trigger)
- [BEFORE INSERT Trigger](https://neon.com/postgresql/postgresql-triggers/postgresql-before-insert-trigger)
- [BEFORE UPDATE Trigger](https://neon.com/postgresql/postgresql-triggers/postgresql-before-update-trigger)
- [AFTER UPDATE Trigger](https://neon.com/postgresql/postgresql-triggers/postgresql-after-update-trigger)
- [BEFORE DELETE Trigger](https://neon.com/postgresql/postgresql-triggers/postgresql-before-delete-trigger)
- [AFTER DELETE Trigger](https://neon.com/postgresql/postgresql-triggers/postgresql-after-delete-trigger)
- [INSTEAD OF Triggers](https://neon.com/postgresql/postgresql-triggers/postgresql-instead-of-triggers)
- [BEFORE TRUNCATE Trigger](https://neon.com/postgresql/postgresql-triggers/postgresql-before-truncate-trigger)
- [Disable Triggers](https://neon.com/postgresql/postgresql-triggers/managing-postgresql-trigger)
- [Enable Triggers](https://neon.com/postgresql/postgresql-triggers/enable-triggers)
- [List All Triggers](https://neon.com/postgresql/postgresql-triggers/how-to-list-all-triggers-in-postgresql)
- [Event Triggers](https://neon.com/postgresql/postgresql-triggers/postgresql-event-trigger)
- [Conditional Triggers](https://neon.com/postgresql/postgresql-triggers/postgresql-trigger-when-condition)