The ALTER TABLE statement attempted to drop a column or index that does not exist, triggering MySQL error 1091.
MySQL Error 1091: ER_CANT_DROP_FIELD_OR_KEY occurs when ALTER TABLE ... DROP targets a column or key that MySQL cannot find. Confirm the object name with SHOW COLUMNS or SHOW INDEX, then rerun the statement with the correct identifier to fix the issue.
Can't DROP '%s'; check that column/key exists
The message "Can't DROP 'object'; check that column/key exists" signals that your ALTER TABLE command references a column, primary key, or secondary index not present in the table definition. MySQL halts DDL execution to protect schema integrity, returning SQLSTATE 42000 and error code 1091.
Error 1091 appears during ALTER TABLE ... DROP COLUMN, DROP INDEX, DROP PRIMARY KEY, or DROP FOREIGN KEY.
It is typical after a schema refactor, merge conflict, or typo where the object was already removed or was never created in the first place.
Unresolved 1091 errors block migration scripts, CI pipelines, and production deploys. Automated tools may stop entirely, increasing downtime risk. Resolving the mismatch keeps your DDL scripts idempotent and your release process predictable.
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A single character typo makes MySQL treat the target as non-existent and raises error 1091.
Running the same DROP statement twice without IF EXISTS causes the second run to fail.
A column or key declared only in some environments may be absent in the current database, triggering the error when dropped unconditionally.
Executing the statement against the wrong schema or similarly named table results in MySQL not finding the object.
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Ignoring it is risky because the rest of the migration may not run. Always confirm the schema state and fix the script.
IF EXISTS for columns and indexes is supported starting in MySQL 8.0. Use procedural checks or dynamic SQL for earlier versions.
Set up a migration dry-run database, run the script, and fail the pipeline on any non-zero exit code from the mysql client.
Galaxy surfaces schema-aware autocomplete and validates ALTER statements against live metadata, catching missing objects before execution.
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