Question

I have a table similar to this:

incident_id    action    action_date
-----------    ------    -----------
    1            A        2012-12-01
    2            A        2012-12-01
    2            Z        2012-12-02
    3            A        2012-12-03
    3            Z        2012-12-04
    3            G        2012-12-05

In the real table there are many more actions and the dates are datetimes.

Here is the result I want:

incident_id    color
-----------    -----
    1          GREEN
    2          RED
    3          BLUE

I’m not sure how to accomplish this, I’m weak with SQL in general.

Oops, sorry for not explaining the colors. Ok if an incident has action A then its green. Action B trumps A and the color then becomes red. And once again action C trumps the others and the color is blue.

Answer 1

You can join onto a (either permanent or derived) table that maps ranks to actions and find the MAX

WITH Actions(action, priority)
     AS (SELECT 'A', 1  UNION ALL
         SELECT 'Z', 2 UNION ALL
         SELECT 'G', 3)
SELECT Y.incident_id,
       CASE MAX(A.priority)
         WHEN 1 THEN 'GREEN'
         WHEN 2 THEN 'RED'
         WHEN 3 THEN 'BLUE'
       END
FROM   YourTable Y
       JOIN Actions A
         ON A.action = Y.action
GROUP  BY Y.incident_id