Converting Oracle SQL Select into PosgreSQL select

Question

I have this SQL statement:

SELECT ABX.ABX_APO_NUMBER,
       COUNT(A1.PROCESS_MODE) AS NUM_PLANNING,
       COUNT(A2.PROCESS_MODE) AS NUM_SETUP,
       COUNT(A3.PROCESS_MODE) AS NUM_OUTPUT
  FROM ABX, USER_INSTANCE U, ACTIVE_PROCESS A1,
       ACTIVE_PROCESS A2, ACTIVE_PROCESS A3
 WHERE U.ABX_APO_NUMBER (+) = ABX.ABX_APO_NUMBER
   AND A1.PROCESS_INSTANCE_NUMBER (+) = U.INSTANCE_NUMBER
   AND A1.PROCESS_MODE (+)= 'PLANNING'
   AND A2.PROCESS_INSTANCE_NUMBER (+) = U.INSTANCE_NUMBER
   AND A2.PROCESS_MODE (+) = 'SETUP'
   AND A3.PROCESS_INSTANCE_NUMBER (+) = U.INSTANCE_NUMBER
   AND A3.PROCESS_MODE (+) = 'OUTPUT'
 GROUP BY ABX.ABX_APO_NUMBER

The (+) is causing fits for PG... Can I just remove those and it will mean the same thing? What would be the equivalent that Postgres would understand?

Answer 1

No, you can not just remove them!

The (+) is the old notation of an OUTER JOIN.

For example

...
  FROM USER_INSTANCE U, ACTIVE_PROCESS A1
 WHERE A1.PROCESS_INSTANCE_NUMBER (+) = U.INSTANCE_NUMBER
   AND A1.PROCESS_MODE (+)= 'PLANNING'
...

would have to be changed to

...
FROM USER_INSTANCE U
LEFT JOIN ACTIVE_PROCESS A1
     ON (     A1.PROCESS_INSTANCE_NUMBER = U.INSTANCE_NUMBER
          AND A1.PROCESS_MODE = 'PLANNING'
        )
...

Answer 2

Here is your query re-written using ANSI-92 JOIN syntax:

  SELECT a.abx_apo_number,
         COUNT(ap1.process_mode) AS NUM_PLANNING,
         COUNT(ap2.process_mode) AS NUM_SETUP,
         COUNT(ap3.process_mode) AS NUM_OUTPUT
     FROM ABX a
LEFT JOIN USER_INSTANCE u ON u.abx_apo_number = a.abx_apo_number
LEFT JOIN ACTIVE_PROCESS ap1 ON ap1.process_instance_number = u.instance_number
                            AND ap1.process_mode = 'PLANNING'
LEFT JOIN ACTIVE_PROCESS ap2 ON ap2.process_instance_number = u.instance_number
                            AND ap2.process_mode = 'SETUP'
LEFT JOIN ACTIVE_PROCESS ap3 ON ap3.process_instance_number = u.instance_number
                            AND ap3.process_mode = 'OUTPUT'
 GROUP BY a.abx_apo_number

The (+) is Oracle specific LEFT OUTER JOIN syntax. To remove it, would require that each USER_INSTANCE.instance_number would have to have values for the process modes being all three: PLANNING, SETUP, and OUTPUT - omit one, and the abx_apo_number would not be displayed in the output.