Question

Is it possible to join the results of 2 sql SELECT statements as one statement where both are query the same tables, and look for values in the same column?

I want to have the id of a task (which is fine) but then I want to filter out certain values into 2 separate columns.

Currently I get get the data in 2 separately:

 SELECT id, string_value as Station FROM table WHERE datatype= 'station'

(column datatype doesn’t need to be seen)

returns something like:

id            Station
task1         station1
task2         station2

and then I have

SELECT id, string_value as RespondingAction FROM table 
 WHERE datatype='RespondingAction'

returning:

id             RespondingAction
task1          Approve
task2          Decline

I want to basically combine these 2 queries, but I’m not sure how as they both look for the data in the same column. Hopefully the end result would be something like this:

id            Station           RespondingAction
task1         station1          Approve
task2         station2          Decline 
task3         station1          Decline
task4         station3          Pending (if null)

Sorry if this isn’t too clear; I’m new to this and trying my best to work this out!

Answer 1

SELECT id, MAX(Station), NVL(Max(RespondingAction), 'Pending')
FROM
  (SELECT id, 
    string_value as Station,
    NULL as RespondingAction
   FROM table
   WHERE dataType = 'station'

   UNION

   SELECT id,
    NULL as Station,
    string_value as RespondingAction
   FROM table
   WHERE dataType = 'RespondingAction')
GROUP By id

EDIT

you can also try to replace

NVL(Max(RespondingAction), 'Pending')

by

   COALESCE(MAX(RespondingAction), CAST('Pending' AS <the type of column string_value>))