<p>MySQL raises error 1546 when a CREATE EVENT or ALTER EVENT statement omits both EVERY and AT in its ON SCHEDULE clause.</p>
<p>MySQL Error 1546: ER_EVENT_NEITHER_M_EXPR_NOR_M_AT appears when an event definition lacks a valid AT timestamp or EVERY interval in the ON SCHEDULE clause. Provide at least one datetime expression or interval to resolve the error.</p>
No datetime expression provided
MySQL throws ER_EVENT_NEITHER_M_EXPR_NOR_M_AT when you run CREATE EVENT or ALTER EVENT without supplying a proper datetime expression. The database expects either an AT timestamp or an EVERY interval in the ON SCHEDULE clause.
The server aborts compilation because it cannot determine when the event should run. Fixing the schedule syntax removes the error instantly.
The error surfaces during event-scheduler statements in MySQL 5.1+ whenever the ON SCHEDULE section is incomplete. It is a pure compile-time syntax problem, not a runtime failure.
Developers often meet it while copying examples, using GUI wizards, or refactoring event code in CI pipelines.
Unscheduled events never execute, breaking data pipelines, cleanup jobs, and reporting tasks. Continuous integration scripts may fail, blocking deployments. Rapid correction keeps automated workflows healthy.
The primary cause is omitting both EVERY and AT within ON SCHEDULE. MySQL therefore cannot parse a valid schedule.
Secondary causes include accidental comment removal, concatenation errors in generated SQL, and misplaced parentheses that hide the schedule tokens.
Always specify at least one scheduling expression. Choose a single run (AT) or a recurring run (EVERY). Validate with SHOW EVENTS before deploying.
Re-run the corrected CREATE EVENT statement or ALTER the existing event to include the missing clause.
During initial creation, add ON SCHEDULE AT '2025-01-01 00:00:00' for one-off tasks. For recurring tasks, use ON SCHEDULE EVERY 1 DAY STARTS CURRENT_TIMESTAMP.
CI scripts generating SQL should template the schedule tokens explicitly to avoid empty strings.
Lint event DDL in code review or a Galaxy SQL notebook. Require automated unit tests that parse event definitions before migration.
Prefer parameterized snippets in Galaxy Collections so the ON SCHEDULE clause is never omitted.
ER_EVENT_CANNOT_DELETE (1548) occurs when attempting to drop a non-existent event. ER_EVENT_INVALID_NAME involves illegal characters in event names. They differ by context but share similar syntax-validation roots.
The developer forgot to include EVERY interval, leaving the schedule empty.
An AT timestamp was intended but removed during editing or commenting.
Dynamic SQL concatenation created ON SCHEDULE with no valid token.
Unbalanced quotes hide the AT or EVERY keyword from the parser.
Raised when trying to DROP an event that does not exist.
Occurs if the event name contains invalid characters or is too long.
Triggered when the EVERY interval uses an unsupported unit.
No. MySQL allows either AT or EVERY, not both. Choose one according to your scheduling needs.
No. It is specific to CREATE EVENT and ALTER EVENT statements.
Enabling the scheduler is necessary for execution, but it does not change the compile-time requirement to supply a datetime expression.
Galaxy’s SQL linting highlights missing AT or EVERY tokens in real time and offers AI fixes before you run the statement.
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