我可以将两个不同表中两列的计数相加吗？

Question

I'm trying to add together the counts of two different tables and group them by the same variable

Here is what I have so far:

SELECT a.storenumber,
       Count (howmanytotal) AS total_counts_store
FROM   (
              SELECT month_counts.howmany,
                     new_counts.howmany) AS howmanytotal
from   (
                  SELECT     a.storenumber,
                             count (b.riid_) AS howmany
                  FROM       $b$ b
                  INNER JOIN $a$ a
                  ON         b.riid_=a.riid_
                  GROUP BY   a.storenumber) month_counts
FROM   (
                  SELECT     a.storenumber,
                             count (c.riid_) AS howmany
                  FROM       $c$ c
                  INNER JOIN $a$ a
                  ON         c.riid_=a.riid_
                  GROUP BY   a.storenumber) new_counts
ON month_counts.storenumber = new_counts.storenumber) theend

where I'm at now:

SELECT howmanytotal AS total_counts_store
FROM   (
              SELECT Count (howmany) AS howmanytotal)
FROM   (
              SELECT month_counts.howmany,
                     new_counts.howmany)
FROM   (
                  SELECT     a.storenumber,
                             count (b.riid_) AS howmany
                  FROM       $b$ b
                  inner join $a$ a
                  ON         b.riid_=a.riid_
                  GROUP BY   a.storenumber) month_counts
UNION
      (
                 SELECT     count (c.riid_) AS howmany
                 FROM       $c$ c
                 inner join $a$ a
                 ON         c.riid_=a.riid_
                 GROUP BY   a.storenumber) new_counts
ON month_counts.storenumber = new_counts.storenumber) ORDER BY $a$.storenumber

Getting this error: Error: java.sql.SQLSyntaxErrorException: ORA-00923: FROM keyword not found where expected Please correct SELECT statement:

Answer 1

Join the subqueries:

select
  storenumber,
  month_counts.howmany as month_count,
  new_counts.howmany as new_count,
  month_counts.howmany + new_counts.howmany as total_count
from (...) month_counts
join (...) new_counts using (storenumber)
order by storenumber;

If it is possible for a storenumber to be missing from one of the subquery results, then outer join and use COALESCE or NVL to deal with the nulls. Here is a query with a full outer join, which is not available in MySQL, but in Oracle and many other DBMS.

select
  storenumber,
  month_counts.howmany as month_count,
  new_counts.howmany as new_count,
  nvl(month_counts.howmany, 0) + nvl(new_counts.howmany, 0) as total_count
from (...) month_counts
full outer join (...) new_counts using (storenumber)
order by storenumber;

Answer 2

Ending up using sum and union to complete. Thank you for your help.

SELECT storenumber,
       SUM(howmany) AS howmanytotal
FROM   (SELECT a.storenumber,
               Count (b.riid_) AS howmany
        FROM   $b$ b
               inner join $a$ a
                       ON b.riid_ = a.riid_
        GROUP  BY a.storenumber
        UNION
        SELECT a.storenumber,
               Count (c.riid_) AS howmany
        FROM   $c$ c
               inner join $a$ a
                       ON c.riid_ = a.riid_
        GROUP  BY a.storenumber)
GROUP  BY storenumber
ORDER  BY storenumber 

This gave me a list of store ids and how many active subscribers we have at each store (taken from two separate tables)