Question

I have a query which shows count of messages received based on dates.
For Eg:

1 | 1-May-2012 
3 | 3-May-2012 
4 | 6-May-2012 
7 | 7-May-2012 
9 | 9-May-2012 
5 | 10-May-2012 
1 | 12-May-2012

As you can see on some dates there are no messages received. What I want is it should show all the dates and if there are no messages received it should show 0 like this

1 | 1-May-2012
0 | 2-May-2012
3 | 3-May-2012
0 | 4-May-2012
0 | 5-May-2012
4 | 6-May-2012
7 | 7-May-2012
0 | 8-May-2012
9 | 9-May-2012
5 | 10-May-2012
0 | 11-May-2012
1 | 12-May-2012

How can I achieve this when there are no rows in the table?

Answer 1

You don’t need a separate table for this, you can create what you need in the query. This works for May:

WITH month_may AS (
    select to_date('2012-05-01', 'yyyy-mm-dd') + level - 1 AS the_date
    from dual
    connect by level < 31
)
SELECT *
  FROM month_may mm
  LEFT JOIN mytable t ON t.some_date = mm.the_date

The date range will depend on how exactly you want to do this and what your range is.