To create a composite foreign key in MySQL, you need to follow these steps:
- Create the primary key in the parent table (referenced table):
CREATE TABLE ParentTable (
PRIMARY KEY (FieldA, FieldB)
- Create the foreign key in the child table (referring table) using the same field names as in the parent table and referencing the primary key in the parent table:
CREATE TABLE ChildTable (
FOREIGN KEY (FieldA, FieldB) REFERENCES ParentTable(FieldA, FieldB)
Note that the data types of the fields in both tables must match. Each field in the child table corresponds to the respective field in the parent table, creating a composite foreign key relationship between them.