[GENERAL] Adding a Foreign key!

Hello everyone, I know that a Primary Key can be added to a table after it has been created, doing this... CREATE UNIQUE INDEX table_pkey ON table (atribute); Well I wonder if a Foreign Key can also be added after the table is already created, and what syntax does it follow. Thankyou

[GENERAL] Adding a Foreign Key

Hello everyone, I know that a Primary Key can be added to a table before it has been created, doing this... CREATE UNIQUE INDEX table_pkey ON table (atribute); Well I wonder if a Foreign Key can also be added and what syntax does it follow. Thankyou in advance. Stay Safe & Happy.