Using MM in Oracle [duplicate] - sql

Question

This question already has an answer here:
Using IW and MM in Oracle
(1 answer)
Closed 9 years ago.
I don't know what's wrong with my query. I just put 'MM' in my query to get the monthly result. But when I run it, it gives me a daily result in 365 days, instead of monthly result. Please help me.
Here's my query:
SELECT 'Data'
|| ',' || TO_CHAR(d.dtime_day, 'MM/dd/yyyy')
|| ',' || NVL(o.cnt_opened, 0) --as cnt_opened
|| ',' || NVL(c.cnt_closed, 0) --as cnt_closed
FROM owner_dwh.dc_date d
LEFT JOIN (
SELECT
TRUNC(t.create_time, 'MM') AS report_date,
count(*) AS cnt_opened
FROM app_account.otrs_ticket t
WHERE t.create_time BETWEEN SYSDATE - 365 AND SYSDATE
GROUP BY TRUNC(t.create_time, 'MM')
) o ON d.dtime_day = o.report_date
LEFT JOIN (
SELECT
TRUNC(t.close_time, 'MM') AS report_date,
count(*) AS cnt_closed
FROM app_account.otrs_ticket t
WHERE t.close_time BETWEEN SYSDATE - 365 AND SYSDATE
GROUP BY TRUNC(t.close_time, 'MM')
) c ON d.dtime_day = c.report_date
WHERE d.dtime_day BETWEEN SYSDATE - 365 AND SYSDATE
ORDER BY d.dtime_day;
Result:
Data,01/25/2013,0,0
Data,01/26/2013,0,0
Data,01/27/2013,0,0
Data,01/28/2013,0,0
Data,01/29/2013,0,0
Data,01/30/2013,0,0

Answer 1

Your initial query against DC_DATE is getting every date in the last 365 days. If you ran just that part:
SELECT 'Data'
||','||TO_CHAR(D.DTIME_DAY,'MM/dd/yyyy')
FROM OWNER_DWH.DC_DATE d
WHERE d.DTIME_DAY BETWEEN SYSDATE -365 AND SYSDATE
ORDER BY D.DTIME_DAY;
... you would expect to get 365 rows returned.
The subqueries you are outer-joining to are only going to return a summary count for the first day of each month. So when you join you will get an actual value (which could be zero) on the first of each month, but always zero on every other date. You could avoid that just by adjusting your where clause, e.g.:
WHERE d.DTIME_DAY BETWEEN SYSDATE -365 AND SYSDATE
AND d.DTIME_DAY = TRUNC(s.DTIME_DAY, 'MM')
The that will only show you the first of each month, and the outer joins will still show dates with zero values if there is no matching data from the subqueries.