MySQL Add constraint foreign key
Add foreign key to MySQL table using alter table syntax and add constraint keyword.
MySQL Add constraint foreign key syntax
ALTER TABLE table_nameB ADD CONSTRAINT constraint_name FOREIGN KEY (column_name) REFERENCES table_nameA (column_name);
Add constraint foreign key example
ALTER TABLE `books` ADD CONSTRAINT fk_product_id FOREIGN KEY (product_id) REFERENCES `products` (id);
Output
table `books` altered.