Re: Sakila database, film_actor table. How do we order them?

[Phillip Ward]

Quote

In first variant I add autoincrement id, as I read somewhere every table need it.

Every Table requires a Primary Key.
What form that Primary Key takes is [still] up for grabs.

These days, it's most common to use a numeric, Surrogate Primary Key (that is meaningless in the Real World). Any other table that references this one only has to specify this one field.

You can also have a Composite Primary key, made up of all the fields needed to make a given record unique which, in this case, would be {film_id, actor_id}.
If another table references this one, then it would have to include both fields, which is another reason the Surrogate Key is so popular.

If you do use a Surrogate Primary Key, then you'll still have to enforce the uniqueness of these two fields, with a [Composite] Unique Index, as in:

create table 
... 
primary key ( id ) 
unique key ( film_id, actor_id )
...

Regards, Phill W.