Question

I have a table that has 2 columns that I’m concerned with

Business_ID   /   Product type

I am trying to write a SQL query to only get businesses that sell one type, but not the others. So the table is populated with

B_ID    prod_type
123  |   A
123  |   A
123  |   B
234  |   A
234  |   C
234  |   C
456  |   A
456  |   D
789  |   A

and the list goes on and on. I am trying to write a SQL statement that will find a B_ID that sells prod_type A and not prod_type B, C, D. Here is what I’m trying but it doesn’t work

SELECT phop_1.Business_id, phop_1.PRODUCT_TYPE, count(*) 
FROM phop phop_1, phop phop_2
WHERE phop_1.Business_id = phop_2.Business_id
  AND phop_1.PRODUCT_TYPE = 'A'
  AND NOT phop_2.PRODUCT_TYPE = 'B'
GROUP BY phop_1.Business_id, phop_1.PRODUCT_TYPE

I also found how to exclude using an outer join, but since it’s the same table I can’t do that unless there is a way to select out the prod_type A before doing the join.

select phop_1.Business_id, phop_1.PRODUCT_TYPE, count(*) 
from phop phop_1
LEFT OUTER JOIN phop phop_2
ON phop_1.Business_id = phop_2.Business_id
WHERE phop_2.Business_id IS NULL
GROUP BY phop_1.Business_id, phop_1.PRODUCT_TYPE

Answer 1

You can try something like this:

SELECT DISTINCT p.BusinessId
FROM phop p
   LEFT JOIN phop p2 ON p.BusinessId = p2.BusinessId AND p2.Product_Type <> 'A'
WHERE p2.BusinessId IS NULL

And the Fiddle.

Good luck.