EC
1544
MySQLERRORNotableEventsHIGH confidence

Event already exists

Production Risk

Low — the event is not modified; use OR REPLACE to update it.

What this means

ER_EVENT_ALREADY_EXISTS (1544, SQLSTATE 42000) is raised when CREATE EVENT is executed for an event name that already exists in the same schema.

Why it happens
  1. 1CREATE EVENT using a name that is already taken by an existing event
  2. 2Running a migration script that creates the event multiple times
How to reproduce
trigger — this will error
trigger — this will error
CREATE EVENT my_event ON SCHEDULE EVERY 1 HOUR DO SELECT 1;
CREATE EVENT my_event ON SCHEDULE EVERY 2 HOUR DO SELECT 2;  -- Duplicate

expected output

ERROR 1544 (42000): Event 'my_event' already exists

Fix

Use CREATE OR REPLACE EVENT or DROP before creating

Use CREATE OR REPLACE EVENT or DROP before creating
-- MySQL 8.0+ supports OR REPLACE:
CREATE OR REPLACE EVENT my_event
  ON SCHEDULE EVERY 1 HOUR
  DO SELECT 1;

-- Or use IF NOT EXISTS:
CREATE EVENT IF NOT EXISTS my_event
  ON SCHEDULE EVERY 1 HOUR
  DO SELECT 1;

Why this works

CREATE OR REPLACE EVENT updates an existing event; IF NOT EXISTS silently skips creation if it already exists.

Version notes
MySQL 8.0

CREATE OR REPLACE EVENT is supported from MySQL 8.0.

Sources
Official documentation ↗

MySQL 8.0 — 1544 ER_EVENT_ALREADY_EXISTS

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