Can MySQL InnoDB Create Foreign Keys Between Tables in Different Databases?

MySQL InnoDB Foreign Key Constraints Across Databases

Can InnoDB within MySQL maintain a foreign key relationship between tables in separate databases?

Answer:

Yes, MySQL allows foreign key constraints to reference tables in different databases.

Implementation:

To establish a cross-database foreign key constraint:

1. Use the otherdb.othertable syntax to specify the referenced table in the foreign key definition.
2. Ensure that both databases are registered and accessible by the MySQL instance using the GRANT command.

For example, to create a foreign key constraint in the mytable table in the mydb database that references the othertable table in the otherdb database, use the following syntax:

ALTER TABLE mydb.mytable
ADD FOREIGN KEY (col1) REFERENCES otherdb.othertable (col2);

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