MySQL returns ER_UNSUPPORTED_ACTION_ON_GENERATED_COLUMN (3106, SQLSTATE HY000) when you run an operation that is not allowed on a generated (computed) column.
ER_UNSUPPORTED_ACTION_ON_GENERATED_COLUMN appears when a statement tries an unsupported change on a generated column, such as adding a foreign key or altering its definition. Change the statement to avoid touching the generated column or convert it to a regular column to resolve the error.
ER_UNSUPPORTED_ACTION_ON_GENERATED_COLUMN
MySQL throws ER_UNSUPPORTED_ACTION_ON_GENERATED_COLUMN (error 3106, SQLSTATE HY000) when a Data Definition Language (DDL) statement attempts an operation that cannot be applied to a generated column. Generated columns are computed from other columns, so certain actions would break their deterministic nature.
The error was introduced in MySQL 5.7.6 when generated columns became a GA feature. It commonly appears during ALTER TABLE commands or index creation involving these virtual or stored columns.
The server checks every DDL statement for compatibility with generated columns. When it sees an action like ADD CONSTRAINT, MODIFY, or REFERENCES that affects a generated column, it aborts the statement and raises error 3106.
The logic protects the integrity of generated values. MySQL limits changes so that computed data remains consistent and deterministic across engine restarts and replication.
First, identify the exact clause targeting the generated column and refactor the statement so it leaves that column untouched. If you must perform the action, convert the column to a regular column and then retry.
Galaxy’s editor surfaces schema metadata next to code, helping you spot which columns are generated and avoid unsupported actions before execution.
Altering a generated column’s definition is forbidden. Instead, drop it and recreate a new generated column with the desired expression.
Adding a foreign key that references a generated column is not allowed. Reference the underlying base columns or add a surrogate key.
Plan generated column definitions early in design. Revisit design rather than altering generated columns later.
Use CHECK constraints on base columns instead of foreign keys on generated ones. Galaxy Collections let teams store proven patterns and flag risky statements for review.
ER_BAD_FIELD_ERROR appears when you reference a non-existent column. Unlike 3106, it is a syntax issue rather than an unsupported action.
ER_GENERATED_COLUMN_NON_PRIOR can occur if a generated column depends on another generated column declared later. Resolve by reordering column definitions.
Generated columns cannot participate in foreign key relationships, so ADD CONSTRAINT fails with 3106.
MySQL disallows direct ALTER COLUMN TYPE on generated fields to prevent expression mismatch.
Partitioning on generated columns is unsupported, triggering the error during CREATE or ALTER TABLE ... PARTITION BY.
ON UPDATE is not valid for generated columns, so attempts raise the same error.
Raised when a generated column refers to an AUTO_INCREMENT column indirectly. Fix by removing circular dependency.
Occurs when a column name is misspelled. Ensure the column exists before running the query.
General message for features MySQL does not yet support, sometimes seen with advanced generated column use cases.
Yes, indexing generated columns is allowed as long as the column expression is deterministic and uses permitted functions.
No. Both virtual and stored generated columns reject unsupported actions with the same error code.
Query INFORMATION_SCHEMA.COLUMNS where EXTRA = 'VIRTUAL GENERATED' or 'STORED GENERATED' to list them.
MySQL 8.0 keeps most rules but adds limited support for CHECK constraints, not for altering generated columns.
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