Jasper reports - grouping

See more:

SQL

I have a query that displays a list or records from the database. E.g.

Mill   Zone   Reading
    
    A      B      22.1
    A      B      NULL
    A      C      33.6
    D      H      11.1
    D      F      56.8

How do I combine the B zone's together and display as following in sql:

Mill   Zone   Reading
    
    A      B      22.1
           C      33.6
    D      H      11.1
           F      56.8

What I have tried:

WITH TEMP_TABLE AS
(SELECT
                                 mz.mill,
                                 sm.sugar_mill_order,
                                 hcz.hczname as ZONE , 
                                 s.name as STATION ,
   round(cast(nvl(d.pvalue,d.dvalue)as float),2) AS Station_Reading,
   round(avg(cast(nvl(d.pvalue,d.dvalue) as float))  over (partition by mz.mill),2) AS Station_Average,
   round(avg(cast(nvl(d.pvalue,d.dvalue) as float)) over (partition by hcz.hczname),2) AS Zone_Average
FROM mill_by_zone mz                   
                    JOIN sugar_mills sm ON sm.sugar_mill_name = mz.mill 
                    JOIN zone_by_station z ON z.zone = mz.zone 
                    JOIN fca_hcz_info hcz ON hcz.hcz = z.zone 
                    JOIN station_details s ON s.station_num = z.station 
                    LEFT OUTER JOIN daily_data d ON s.station_num = d.station_num AND d.recorded = to_date('01/APR/2019', 'dd/mon/yyyy') AND d.dcode =  8
GROUP BY  mz.mill, sm.sugar_mill_order,hcz.hczname, s.name, d.dvalue, d.pvalue, d.dcode
ORDER BY sm.sugar_mill_order, hcz.hczname,Station_Reading
),

      TEMP_TABLE2 AS 
                  (SELECT 
                   round(avg(cast(nvl(d.pvalue,d.dvalue) as float)),2) AS Average_For_Report
                   FROM mill_by_zone mz 
                   JOIN sugar_mills sm ON sm.sugar_mill_name = mz.mill 
                   JOIN zone_by_station z ON z.zone = mz.zone 
                   JOIN fca_hcz_info hcz ON hcz.hcz = z.zone 
                   join station_details s ON s.station_num = z.station 
                   LEFT OUTER JOIN daily_data d ON s.station_num = d.station_num AND d.recorded = to_date('01/APR/2019', 'dd/mon/yyyy') AND d.dcode =  8 
                    )
                   
 SELECT * FROM TEMP_TABLE, TEMP_TABLE2;