Question

I have an query that has been giving me trouble. I think there is probably an easy solution, but please help me where you can!

My main problem is that there are often multiple emails per cust_id. There are unique identifiers such as a sequence number (seq_no) and updated date (updated_date). I only want the newest email address to show for any one customer.

By the way, this is an oracle DB.

Any suggestions?

SELECT DISTINCT
table1.indident_id, 
table1.incident_detail_id, 
table1.incdent_entered_date, 
table1.entering_employee, 
table2.EMAIL
FROM table1
left outer join table2 on table1.cust_id=table2.cust_id
WHERE table1.incdent_entered_date>=current_date-4
AND table1.table1.incident_detail_id=(select min(table1.table1.incident_detail_id)from table1)
AND table2.EMAIL NOT IN ('NONE','none','[e-mail]')
AND table2.EMAIL like '%@%'

Answer 1

A couple of options. The most efficient is to use an analytic function.

SELECT *
  FROM (
    SELECT table1.indident_id, 
           table1.incident_detail_id, 
           table1.incdent_entered_date, 
           table1.entering_employee, 
           table2.EMAIL,
           row_number() over (partition by table2.cust_id
                                  order by table2.updated_date desc) rnk
      FROM table1 
           left outer join table2 on table1.cust_id=table2.cust_id
     WHERE table1.incdent_entered_date>=current_date-4
       AND table1.table1.incident_detail_id=(select min(table1.table1.incident_detail_id)
                                               from table1)
       AND table2.EMAIL NOT IN ('NONE','none','[e-mail]')
       AND table2.EMAIL like '%@%'
  )
 WHERE rnk = 1

Less efficiently, but something that will work in just about any database, would be to do something similar to what you’re currently doing with the incident_detail_id subquery

    SELECT table1.indident_id, 
           table1.incident_detail_id, 
           table1.incdent_entered_date, 
           table1.entering_employee, 
           table2.EMAIL
      FROM table1 
           left outer join table2 on table1.cust_id=table2.cust_id
     WHERE table1.incdent_entered_date>=current_date-4
       AND table1.table1.incident_detail_id=(select min(table1.table1.incident_detail_id)
                                               from table1)
       AND table2.update_date = (SELECT MAX(t2_inner.update_date)
                                   FROM table2 t2_inner
                                  WHERE t2_inner.cust_id = table1.cust_id)
       AND table2.EMAIL NOT IN ('NONE','none','[e-mail]')
       AND table2.EMAIL like '%@%'