Why is it more efficient to create two tables vs one?

Question

Re: "Rather than storing the customer name in both tables, the orders table contains a reference to the customer ID that appears in the customers table. This approach is more efficient, as opposed to storing the same text values in both tables."

Answer 1

Imagine you have a `customer` table with 20 or so columns (address, name, ...), and a table `who_bought_what`:

customer_id, object_id
1, 14828
1, 48220
1, 58338

So customer 1 bought three things and by storing only the ID instead of the whole customer, you don't have to put the same 20 values into your table three times.

Saves a lot of space. Later on you can join the tables if you need to.

Answer 2

Of course! Thanks!