Aggregate from two tables

Question

Dear all,
I have a need to compare totals from 2 tables.
The table data is as follows :
create table FLIGHTS( PSGRNAME VARCHAR2(64), FLTNBR VARCHAR2(5),
FLTDATE DATE, NBRINPARTY NUMBER ) ;
insert into FLIGHTS (PSGRNAME, FLTNBR, FLTDATE, NBRINPARTY)
values ('SMITH/AMR/BMRS', '001', to_date('20-10-2010', 'dd-mm-yyyy'), 2);
insert into FLIGHTS (PSGRNAME, FLTNBR, FLTDATE, NBRINPARTY)
values ('BROWN/CMR', '003', to_date('20-10-2010', 'dd-mm-yyyy'), 1);
insert into FLIGHTS (PSGRNAME, FLTNBR, FLTDATE, NBRINPARTY)
values ('GREEN/AMR/BMRS/CMISS', '001', to_date('20-10-2010', 'dd-mm-yyyy'), 3);
insert into FLIGHTS (PSGRNAME, FLTNBR, FLTDATE, NBRINPARTY)
values ('DOE', '002', to_date('20-10-2010', 'dd-mm-yyyy'), 1);
insert into FLIGHTS (PSGRNAME, FLTNBR, FLTDATE, NBRINPARTY)
values ('MILLER/DMR/CMISS', '002', to_date('20-10-2010', 'dd-mm-yyyy'), 2);
insert into FLIGHTS (PSGRNAME, FLTNBR, FLTDATE, NBRINPARTY)
values ('TAYLOR/RMR/TMRS/AMSTR/BMSTR', '002', to_date('20-10-2010', 'dd-mm-yyyy'), 4);
create table MEALS ( PSGRNAME VARCHAR2(64), FLTNBR VARCHAR2(5),
FLTDATE DATE, MEALTYPE VARCHAR2(4), NBRINPARTY NUMBER ) ;
insert into MEALS (PSGRNAME, FLTNBR, FLTDATE, MEALTYPE, NBRINPARTY)
values ('SMITH/AMR', '001', to_date('20-10-2010', 'dd-mm-yyyy'), 'VGML', 1);
insert into MEALS (PSGRNAME, FLTNBR, FLTDATE, MEALTYPE, NBRINPARTY)
values ('BROWN/CMR', '001', to_date('20-10-2010', 'dd-mm-yyyy'), 'SFML', 1);
insert into MEALS (PSGRNAME, FLTNBR, FLTDATE, MEALTYPE, NBRINPARTY)
values ('TAYLOR/BMSTR', '002', to_date('20-10-2010', 'dd-mm-yyyy'), 'CHML', 1);
I need to compare the total bookings against count of people who had a meal request. The result would look like this
FLTDATE FLTNBR PSGR_COUNT MEAL_COUNT
10/20/2010 001 5 2
10/20/2010 002 7 1
10/20/2010 003 1 0
I tried searching the forum and internet in general and found this : http://www.dba-oracle.com/t_convert_set_to_join_sql_parameter.htm
However, I could not understand the article fully. Hope someone here can help me here with an example query which I can translate to the real data.
Oracle version is 10g.
Both tables contain around 10 million or more records.
Regards
Crusoe
Edited by: Crusoe on Oct 21, 2010 1:57 PM

Answer 1

Hi,
Where Mustafa used COUNT (*), just use SUM (nbrinparty) instead.
Also, you need to GROUP BY both fltnbr and fltdate, and join by both columns as well.
Since there can be flights with no meals (like fltnbr 003), the join has to be an outer join.
So what you want is something like:
SELECT      f.fltdate
,      f.fltnbr
,      flight_total
,      NVL (meal_total, 0)     AS meal_total
FROM       (
          SELECT        fltdate,  fltnbr
          ,       SUM (nbrinparty)      AS meal_total
          FROM       meals
          GROUP BY  fltdate,  fltnbr
     ) m
          SELECT       fltdate,  fltnbr
          ,       SUM (nbrinparty)      AS flight_total
          FROM       flights
          GROUP BY  fltdate,  fltnbr
     ) f
WHERE     m.fltdate (+)      = f.fltdate
AND     m.fltnbr  (+)     = f.fltnbr;Alternatively, you could do just one sub-query, to get the sum from either one of the tables. In the main query, get the sum from the other table and join, like this:
ITH     got_meal_total     AS
     SELECT        fltdate,  fltnbr
     ,       SUM (nbrinparty)      AS meal_total
     FROM       meals
     GROUP BY  fltdate,  fltnbr
SELECT      f.fltdate
,      f.fltnbr
,      SUM (f.nbrinparty)          AS flight_total
,      NVL (SUM (m.meal_total), 0)     AS meal_total
FROM           flights        f
LEFT OUTER JOIN  got_meal_total      m  ON       f.fltdate     = m.fltdate
                             AND   f.fltnbr     = m.fltnbr
GROUP BY  f.fltdate
,       f.fltnbr
;Edited by: Frank Kulash on Oct 21, 2010 6:52 AM
Added one-sub-query option