3206
MariaDBERRORNotableDDLHIGH confidence
Invalid foreign key option for generated column
Production Risk
Low — DDL error.
Why it happens
- 1Defining a foreign key constraint on a virtual generated column.
- 2FK actions like ON UPDATE SET NULL or ON DELETE CASCADE are incompatible with generated columns.
How to reproduce
trigger — this will error
trigger — this will error
ALTER TABLE t1 ADD CONSTRAINT fk1 FOREIGN KEY (gen_col) REFERENCES t2(id) ON UPDATE SET NULL;
expected output
ERROR 3206 (HY000): Foreign key constraint on a generated column not allowed with this option.
Fix 1
Use a stored generated column if FK is required
Use a stored generated column if FK is required
ALTER TABLE t1 MODIFY gen_col INT AS (expr) STORED;
Why this works
Stored generated columns have fewer FK restrictions than virtual ones.
Fix 2
Remove incompatible ON UPDATE/ON DELETE clauses
Remove incompatible ON UPDATE/ON DELETE clauses
ALTER TABLE t1 ADD CONSTRAINT fk1 FOREIGN KEY (gen_col) REFERENCES t2(id);
Why this works
Simple FK references without cascade actions may work on stored generated columns.
What not to do
✕
Sources
Official documentation ↗
MySQL 8.0 — 3206 ER_WRONG_FK_OPTION_FOR_GENERATED_COLUMN3
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