How to add foreign keys in MySQL?

The foreign key is used to link one or more tables together. We can add a foreign key to a table in two ways:

1. Using the CREATE TABLE statement
2. Using the ALTER TABLE statement

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Following is the syntax to ?create foreign key using CREATE TABLE OR ALTER TABLE statement:

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[CONSTRAINT?constraint_name]????

??? FOREIGN?KEY?[foreign_key_name]?(col_name,?...)????

??? REFERENCES?parent_tbl_name?(col_name,...)???