Report for every 1 hour

Question

I wanted to take out a report for every one hour, the count, i used trunc(x_date,'hh24') to take the report, but the problem is, for few hours there wont be any count, so i have to substitute with zero there, any ideas ?,

Answer 1

Hi,
If you want to make sure all hours appear in the result set, even if they don't appear in the table, then outer-join to a table (or, in the example below, a sub-query) where you know they do exist.
For example, if your table_x has columns entry_dt and amt, and you want results for every hour of the day, you can do somehting like this:
WITH     all_hours     AS
     SELECT     TO_CHAR ( SYSDATE + (LEVEL / 24)
               , 'HH24'
               )     AS hr
     FROM     dual
     CONNECT BY     LEVEL     <= 24
SELECT       a.hr
,       COUNT (entry_dt)     AS cnt
,       NVL ( AVG (amt)
           , 0
           )               AS avg_amt
FROM           all_hours  a
LEFT OUTER JOIN      table_x    x      ON   a.hr = TO_CHAR (entry_dt, 'HH24')
GROUP BY  a.hr
ORDER BY  a.hr
;COUNT never returns NULL, so you don't have to use NVL with COUNT.
For other aggregate functions (such as AVG) you do need to use NVL to get 0 instead of NULL.
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only), and the results you want from that data.
Explain, using specific examples, how you get those results from that data.
Always say what version of Oracle you're using.