<p>MySQL cannot add a foreign key constraint to a system table or data dictionary entry, blocking the ALTER or CREATE operation.</p>
<p>MySQL Error 1823 ER_FK_FAIL_ADD_SYSTEM appears when the server fails to add a foreign key to a system table, usually mysql.* or data dictionary objects. Avoid referencing system tables, correct column definitions, run mysql_upgrade if needed, and retry the operation on a regular InnoDB table to resolve the issue.</p>
Failed to add the foreign key constraint '%s' to system
The error message Failed to add the foreign key constraint '%s' to system tells you that MySQL tried to register a new foreign key inside its internal system catalog, but the operation violated system-table rules. The server stops the DDL statement to protect the data dictionary from corruption.
The error surfaces during CREATE TABLE, ALTER TABLE, or IMPORT TABLESPACE statements that define or revalidate a foreign key. It is most common when the referenced or referencing table is located in a system schema such as mysql, performance_schema, or sys, or when the data dictionary is out of sync after an upgrade or crash.
Leaving the error unresolved blocks schema migrations, breaks application deployments, and may hide deeper dictionary inconsistencies. Quickly resolving Error 1823 ensures referential integrity, keeps CI/CD pipelines green, and prevents unexpected downtime in production environments.
Creating a foreign key that points to or originates from a table in the mysql, sys, or performance_schema databases triggers the error because MySQL forbids foreign keys on system objects.
A table moved out of the mysql schema without a full cleanup remains flagged as a system table in the data dictionary, causing foreign key registration to fail.
An interrupted upgrade or crash can leave inconsistent metadata so any attempt to add a constraint to the affected table raises Error 1823.
If the parent and child columns differ in type, length, or charset, the engine may reject the constraint at the system-table stage instead of the syntax stage.
Users without ALTER or REFERENCES rights on a system table may trigger the error because MySQL cannot complete the dictionary update.
Generic InnoDB message shown when the issue is in user tables, not system tables. Similar troubleshooting but does not involve protected schemas.
Raised when validating an existing foreign key fails. Often follows if Error 1823 is ignored and metadata gets corrupted.
Occurs when altering a column referenced by a foreign key without dropping the constraint first.
In most cases yes, but any table flagged as system in the data dictionary can trigger it, even if it now lives in a user schema.
No. MySQL blocks foreign keys on system tables by design. Move your data to a regular schema.
An upgrade alone may not solve it, but running mysql_upgrade after the version change often cleans corrupted dictionary entries that cause the error.
Galaxy's context-aware AI flags attempts to reference system tables and suggests correct syntax, preventing the invalid DDL from reaching your database.
.avif)
.avif){kind=logo}
