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23 wrz 2013 · Your foreign key on movieCode should be on the roll table. MovieCode is the primary key of the movie table.
You can obtain information specific to InnoDB foreign keys from the INNODB_FOREIGN and INNODB_FOREIGN_COLS tables. Example queries are show here:
The INNODB_FOREIGN table has these columns: The name (not a numeric value) of the foreign key index, preceded by the schema (database) name (for example, test/products_fk). The name of the child table in this foreign key relationship. The name of the parent table in this foreign key relationship. The number of columns in the foreign key index.
3 lut 2024 · As of MySQL 5.x, InnoDB is the only MySQL database engine that supports foreign keys. (You might be able to use the foreign key syntax with other MySQL database engines, but InnoDB is the only database engine that actually uses the information you define in your CREATE TABLE statements.)
SET NULL: Delete or update the row from the parent table, and set the foreign key column or columns in the child table to NULL. Both ON DELETE SET NULL and ON UPDATE SET NULL clauses are supported. If you specify a SET NULL action, make sure that you have not declared the columns in the child table as NOT NULL.
InnoDB supports foreign keys that allow you to create relationships between tables and enforce referential integrity in the database. The foreign key support is crucial for maintaining data consistency.
To maintain data integrity, InnoDB supports FOREIGN KEY constraints. With foreign keys, inserts, updates, and deletes are checked to ensure they do not result in inconsistencies across related tables.
