>
> Beware: Fieldnames in the queries must be different, except for C. If
> this is not acceptable, you must add a join condition rather than
> making it NATURAL.
If NATURAL keyword is not supported by your DBMS, you also need to add
join conditions.
Note: You must use coalesce functions in second and subsequent join
conditions.
Like this:
SELECT coalesce(t1.c,t2.c,t3.c)
,"Count_in_T_1"
,"Count_in_T_2"
,"Count_in_T_3"
FROM
(SELECT C, count(*) as "Count_in_T_1" FROM T_1 GROUP BY C) AS t1
FULL OUTER JOIN
(SELECT C, count(*) as "Count_in_T_2" FROM T_2 GROUP BY C) AS t2
ON t2.c = t1.c
FULL OUTER JOIN
(SELECT C, count(*) as "Count_in_T_3" FROM T_3 GROUP BY C) AS t3
ON t3.c = coalesce(t1.c, t2.c)
Received on Wed Aug 07 2002 - 07:35:24 CDT
