Question

I’m trying to select customer names with the same zip code but I can’t seem to get the correct result. The correct rows that are meant to be returned are 11. I seem to be getting 14 using the following:

SELECT a.customer_first_name, a.customer_last_name, a.customer_zip FROM customers a
UNION
SELECT b.customer_first_name, b.customer_last_name, b.customer_zip FROM customers b

From here I’m kinda stuck. I know that both statements are the same but this is the basis of where I got to.

I was going to use something along the lines of:

WHERE a.customer_zip=b.customer_zip

But of course this doesn’t work and is kind of irrelevant.

Customers table:

Any help would be much appreciated. If I’ve missed anything and/or this comes across unclear, then I apologise. Thanks.

Edit: The correct result should be 11 rows (which I can’t seem to achieve).

Answer 1

SELECT customer_first_name, customer_last_name, customer_zip
FROM customers where customer_zip in 
  (SELECT customer_zip FROM customers
   GROUP BY customer_zip
   HAVING COUNT(*) > 1);