surrogate keys as foreign key

Question

Is setting the foreign key as surrogate of the parent table expense ?

Since I have to join that parent /reference table to show the natural key.

But why it is the best to set the foreign key as surrgate for referencing table.

Answer 1

It is expensive in a sense that you'd need a JOIN in some situations where it would not be necessary with the natural key (as you already noted). Also, natural keys usually play better with clustering , and are sometimes necessary for correctly modelling diamond-shaped dependencies .

On the other hand, using a "skinnier" surrogate key can save some space and simplify updating (especially when there are several levels of FKs).

Neither approach is absolutely "better" - It's a matter of compromise.