CREATE DATABASE db1;
USE db1;
CREATE TABLE t1 (val INT);
CREATE TRIGGER IF NOT EXISTS val_sum BEFORE INSERT ON t1 FOR EACH ROW SET @sum = @sum + NEW.val;
SET @sum=0;
INSERT INTO t1 VALUES (10), (20), (30);
SELECT @sum;
@sum
60
CREATE TRIGGER IF NOT EXISTS val_sum_new BEFORE INSERT ON t1 FOR EACH ROW SET @sum = @sum + NEW.val;
CREATE TRIGGER IF NOT EXISTS val_sum AFTER INSERT ON t1 FOR EACH ROW SET @sum = @sum + 1 + NEW.val;
Warnings:
Note	1359	Trigger 'db1.val_sum' already exists
CREATE OR REPLACE TRIGGER IF NOT EXISTS val_sum BEFORE INSERT ON t1 FOR EACH ROW SET @sum = @sum + 2 + NEW.val;
ERROR HY000: Incorrect usage of OR REPLACE and IF NOT EXISTS
SELECT ACTION_STATEMENT FROM INFORMATION_SCHEMA.TRIGGERS WHERE TRIGGER_NAME='val_sum';
ACTION_STATEMENT
SET @sum = @sum + NEW.val
CREATE OR REPLACE TRIGGER val_sum BEFORE INSERT ON t1 FOR EACH ROW SET @sum = @sum + 3 + NEW.val;
SELECT ACTION_STATEMENT FROM INFORMATION_SCHEMA.TRIGGERS WHERE TRIGGER_NAME='val_sum';
ACTION_STATEMENT
SET @sum = @sum + 3 + NEW.val
CREATE TRIGGER val_sum BEFORE INSERT ON t1 FOR EACH ROW SET @sum = @sum + 4 + NEW.val;
ERROR HY000: Trigger 'db1.val_sum' already exists
SELECT ACTION_STATEMENT FROM INFORMATION_SCHEMA.TRIGGERS WHERE TRIGGER_NAME='val_sum';
ACTION_STATEMENT
SET @sum = @sum + 3 + NEW.val
# Clearing up
DROP TRIGGER IF EXISTS val_sum;
SELECT ACTION_STATEMENT FROM INFORMATION_SCHEMA.TRIGGERS WHERE TRIGGER_NAME='val_sum';
ACTION_STATEMENT
DROP TRIGGER IF EXISTS val_sum;
Warnings:
Note	1360	Trigger does not exist
DROP TABLE t1;
DROP DATABASE db1;