# Foreign Key
A Foreign key is a [[Constraint]] that protects links between tables. Foreign key is a attribute or attributes that link to the [[Primary Key]] of a other entity set (table).

## Example
Authors 
|ID (PK)|Name|Age|Sex|Length|   
|-----|-----|-----|-----|-----|
|1|Nick|21|M|190|
Authors 
|ID (PK)|Job|Age|Sex|Length|
|-----|-----|-----|-----|-----|
|1|Nick|21|M|190|