Question

How do you exclude a set of values when using a left outer join?

Consider the following query:

SELECT i.id,
       i.location,
       area.description
  FROM incident_vw i,
       area_vw area
 WHERE i.area_code = area.code(+)
   AND i.area_code NOT IN ('T20', 'V20B', 'V20O', 'V20P')

The query executes, yet none of the NULL area code values appear.

BE AWARE: INCIDENT_VW.area_code can and does have NULL values.

Any ideas on how to match NULL incident area codes while excluding the given set of area codes, without using PL/SQL?

ANSI Update

Using the equivalent ANSI SQL also does not work:

    SELECT i.id,
           i.location,
           area.description
      FROM incident_vw i
 LEFT JOIN area_vw area
        ON area.code = i.area_code
     WHERE i.area_code NOT IN ('T20', 'V20B', 'V20O', 'V20P')

Solution

This works:

SELECT i.id,
       i.location,
       area.description
  FROM incident_vw i,
       area_vw area
 WHERE i.area_code = area.code(+)
   AND (i.area_code NOT IN ('T20', 'V20B', 'V20O', 'V20P') and i.area_code IS NULL)

Thanks everyone!

Answer 1

Seems the problem is the IN is removing all the area_codes that are NULL.

Give this a try:

    SELECT i.id,
           i.location,
           area.description
      FROM incident_vw i
 LEFT JOIN area_vw area
        ON area.code = i.area_code
     WHERE (i.area_code NOT IN ('T20', 'V20B', 'V20O', 'V20P')
            OR i.area_code IS NULL)

Should give the desired result…