Below are the differences between Primary Key and Foreign Key.
| Primary Key || Foreign Key |
| It will not allow NULL values. || It will allow NULL values. |
| Primary Key can not contain duplicate values. || Foreign Key allows duplicate values. |
| A table can have only one Primary Key. || A table can have multiple Foreign Keys. |
| Clustered index will be created by defauult. || Index will not be created automatically, need to be created manually. |