Aggregation query

Question

Dear colleagues,
I would like to create the query that:
1 step: find the max of NSAVERAGE per day
2 step: max of "1st step" per NE & LAC
My tables:
A. Table "SUB"
Name Null? Type
MSC_ID NUMBER
LAC_ID NUMBER
PERIOD_START_TIME DATE
PERIOD_DURATION NUMBER
NSCURRENT NUMBER
NSAVERAGE NUMBER
B. Table NE_ID
Name Null? Type
NE_ID NUMBER
NE_NAME VARCHAR2(10)
For the 1st step I created the following query:
SELECT n.ne_name AS "MSS",
s.LAC_ID,
TO_CHAR(s.PERIOD_START_TIME,'DD.MM.YYYY') AS "DATE",
MAX(s.NSAVERAGE) AS "MAX_SUB"
FROM ne_id n JOIN SUB s
ON (n.ne_id = s.msc_id)
WHERE MOD(TO_CHAR(s.period_start_time,'J'),7)+1 ----- the weekend values are excluded
IN (1,2,3,4,5)
GROUP BY n.ne_name, s.LAC_ID, TO_CHAR(s.PERIOD_START_TIME,'DD.MM.YYYY')
ORDER BY s.LAC_ID ASC;
and now I'd like to create 2nd step: let's say, to get max of max from step1 grouped by ne_name & LAC
Could you please help how to modify my query?
Thanks
Lukasz

Answer 1

might be easier for people to work on your problem if you post your source data as either insert statments or a with t kind of construct.
WITH t
     AS (SELECT 'M1' mss,
                1 lac,
                TO_DATE ('2012/07/06 12:00:00', 'yyyy/mm/dd HH24:MI:SS')
                   period_start_time,
                100 nsaverage
           FROM DUAL
         UNION ALL
         SELECT 'M1',
                1,
                TO_DATE ('2012/07/06 1300:00', 'yyyy/mm/dd HH24:MI:SS'),
                150
           FROM DUAL
         UNION ALL
         SELECT 'M1',
                1,
                TO_DATE ('2012/07/06 1400:00', 'yyyy/mm/dd HH24:MI:SS'),
                200
           FROM DUAL
         UNION ALL
         SELECT 'M1',
                1,
                TO_DATE ('2012/07/07 1200:00', 'yyyy/mm/dd HH24:MI:SS'),
                110
           FROM DUAL
         UNION ALL
         SELECT 'M1',
                1,
                TO_DATE ('2012/07/07 1300:00', 'yyyy/mm/dd HH24:MI:SS'),
                100
           FROM DUAL
         UNION ALL
         SELECT 'M1',
                1,
                TO_DATE ('2012/07/07 1400:00', 'yyyy/mm/dd HH24:MI:SS'),
                120
           FROM DUAL
         UNION ALL
         SELECT 'M1',
                2,
                TO_DATE ('2012/07/06 1200:00', 'yyyy/mm/dd HH24:MI:SS'),
                100
           FROM DUAL
         UNION ALL
         SELECT 'M1',
                2,
                TO_DATE ('2012/07/06 1300:00', 'yyyy/mm/dd HH24:MI:SS'),
                120
           FROM DUAL
         UNION ALL
         SELECT 'M1',
                2,
                TO_DATE ('2012/07/06 1400:00', 'yyyy/mm/dd HH24:MI:SS'),
                200
           FROM DUAL
         UNION ALL
         SELECT 'M1',
                2,
                TO_DATE ('2012/07/07 1200:00', 'yyyy/mm/dd HH24:MI:SS'),
                180
           FROM DUAL
         UNION ALL
         SELECT 'M1',
                2,
                TO_DATE ('2012/07/07 1300:00', 'yyyy/mm/dd HH24:MI:SS'),
                160
           FROM DUAL
         UNION ALL
         SELECT 'M1',
                2,
                TO_DATE ('2012/07/07 1400:00', 'yyyy/mm/dd HH24:MI:SS'),
                150
           FROM DUAL
         UNION ALL
         SELECT 'M2',
                1,
                TO_DATE ('2012/07/06 1200:00', 'yyyy/mm/dd HH24:MI:SS'),
                100
           FROM DUAL
         UNION ALL
         SELECT 'M2',
                1,
                TO_DATE ('2012/07/06 1300:00', 'yyyy/mm/dd HH24:MI:SS'),
                150
           FROM DUAL
         UNION ALL
         SELECT 'M2',
                1,
                TO_DATE ('2012/07/06 1400:00', 'yyyy/mm/dd HH24:MI:SS'),
                200
           FROM DUAL
         UNION ALL
         SELECT 'M2',
                1,
                TO_DATE ('2012/07/07 1200:00', 'yyyy/mm/dd HH24:MI:SS'),
                110
           FROM DUAL
         UNION ALL
         SELECT 'M2',
                1,
                TO_DATE ('2012/07/07 1300:00', 'yyyy/mm/dd HH24:MI:SS'),
                100
           FROM DUAL
         UNION ALL
         SELECT 'M2',
                1,
                TO_DATE ('2012/07/07 1400:00', 'yyyy/mm/dd HH24:MI:SS'),
                120
           FROM DUAL
         UNION ALL
         SELECT 'M2',
                2,
                TO_DATE ('2012/07/06 1200:00', 'yyyy/mm/dd HH24:MI:SS'),
                100
           FROM DUAL
         UNION ALL
         SELECT 'M2',
                2,
                TO_DATE ('2012/07/06 1300:00', 'yyyy/mm/dd HH24:MI:SS'),
                120
           FROM DUAL
         UNION ALL
         SELECT 'M2',
                2,
                TO_DATE ('2012/07/06 1400:00', 'yyyy/mm/dd HH24:MI:SS'),
                200
           FROM DUAL
         UNION ALL
         SELECT 'M2',
                2,
                TO_DATE ('2012/07/07 1200:00', 'yyyy/mm/dd HH24:MI:SS'),
                180
           FROM DUAL
         UNION ALL
         SELECT 'M2',
                2,
                TO_DATE ('2012/07/07 1300:00', 'yyyy/mm/dd HH24:MI:SS'),
                160
           FROM DUAL
         UNION ALL
         SELECT 'M2',
                2,
                TO_DATE ('2012/07/07 1400:00', 'yyyy/mm/dd HH24:MI:SS'),
                150
           FROM DUAL)