Get user count from two tables and display in 1 row

Question

I have 2 tables.....
Table1 Table2
user date user date
With 1 query, I want to display the user, the count of the number of times a user appears in Table1.user as count1 and the count of the number of times that same user appears in Table2.user as count2 between a specific time period. I have looked and tried things including joins, unions, nested loops but can't get anything to work. The result would appear like this:
USER COUNT1 COUNT2
john 100 2
doe 1000 200
Thank you for your time. I'm really stuck and confused.

Answer 1

Hi,
Welcome to the forum!
I think the easiest way to do this is to do a GROUP BY query on each table separately, and then combine the results, using FULL OUTER JOIN or UNION.
WITH     union_data     AS
     SELECT       user_name
     ,       COUNT (*)     AS count1
     ,       0              AS count2
     FROM       table1
     WHERE       dt     >= &start_dt
     AND       dt      <  &end_dt + 1
     GROUP BY  user_name                             -- Forgot this originally!
UNION ALL
     SELECT       user_name
     ,       0              AS count1
     ,       COUNT (*)     AS count2
     FROM       table2
     WHERE       dt     >= &start_dt
     AND       dt      <  &end_dt + 1     
     GROUP BY  user_name                             -- Forgot this originally!
SELECT       user_name
,       SUM (count1)     AS count1
,       SUM (count2)     AS count2
FROM       union_data
GROUP BY  user_name
;Edited by: Frank Kulash on Jul 29, 2009 1:34 PM
Edited by: Frank Kulash on Jul 29, 2009 2:46 PM
As Solomon pointed out, I forgot the GROUP BY clauses in the sub-query.
Without the tables, I can't test it.