Select all records from one table not in another table based on a condition

Question

I have a customers table t1 which looks like this:

cust_id    cust_zip
   1000      19999
   2000      29999
   4000      39999
   5000      89999

I have a transactions table t2 that looks like this:

store_id    cust_id    cust_zip
     100       1000       19999
     100       2000       29999
     100       3000       39999

I'm trying to pull t2.store_id , t2.cust_zip and t1.cust_id into one table where:

1. the cust_zip field matches
2. cust_id field does not match

The result I'm looking for is:

store_id    cust_zip    cust_id
     100       39999       4000

In this example, cust_id 5000 is not pulled from t1 because the associated cust_zip 89999 is not associated with store_id 100 in t2 . What's the best way to do this?

Answer 1

Have you tried a simple conditional join?

Select t2.store_id,t2.cust_zip,t1.cust_id
from t2
join t1 on t2.cust_zip=t1.cust_zip and t2.cust_id<>t1.cust_id

I do wonder though why your database is not normalized. I would think transaction table would probably have store_zip then you are trying to match store zip with customer zip

Answer 2

Sounds like a JOIN and a WHERE query. Something like this: (query might be different depending on your SQL dialect)

SELECT t2.store_id, t2.cust_zip, t1.cust_id FROM t1
JOIN t2 ON t1.cust_zip = t2.cust_zip
WHERE t1.cust_zip = t2.cust_zip AND
      t1.cust_id != t2.cust_id