Count Distinct over a Window

Question

Hi everyone,
An analyst on my team heard of a new metric called a "Stickiness" metric. It basically measures how often users are coming to your website overtime.
The definition is as follows:
# Unique Users Today/#Unique users Over Last 7 days
and also
# Unique Users Today/#Unique users Over Last 30 days
We have visit information stored in a table W_WEB_VISIT_F. For the sake of simplicity say it has columns VISIT_ID, VISIT_DATE and USER_ID (there are several more dimensional columns it has but I want to keep this exercise simple).
I want to create an aggregate table called W_WEB_VISIT_A that pre-aggregates the three values I need per day: # Unique Users Today, #Unique users Over Last 7 days and #Unique users Over Last 30 days. The only way I can think of building the aggregate table is as follows
WITH AGG AS (
SELECT
VISIT_DATE,
USER_ID
FROM W_WEB_VISIT_F
GROUP BY
VISIT_DATE,
USER_ID
select
VISIT_DATE
COUNT(DISTINCT USER_ID) UNIQUE_TODAY,
(select count(distinct hist.USER_ID) from agg hist where hist.VISIT_DATE between src.VISIT_DATE - 6 and src.VISIT_DATE) SEVEN_DAYS,
(select count(distinct hist.USER_ID) from agg hist where hist.VISIT_DATE between src.VISIT_DATE - 29 and src.VISIT_DATE) THIRTY_DAYS
from agg
group by visit_date
The problem I am having is that W_WEB_VISIT_F has several million records in it and I can't get it the above query to complete. It ran over night and didn't complete.
Is there a fancy 11g function I can use to do this for me? Is there a more efficient method?
Thanks everyone for the help!
-Joe
Edited by: user9208525 on Jan 13, 2011 6:24 AM
You guys are right. I missed the group by I had in the WITH Clause.

Answer 1

Hi,
Haven't used the windowing clause a lot, so I wanted to give a try.
I made up some data with this query :create table t as select sysdate-dbms_random.value(0,10) visit_date, mod(level,5)+1 user_id
from dual
connect by level <= 20;Which gave me following rows :Scott@my10g SQL>select * from t order by visit_date;
VISIT_DATE             USER_ID
03/01/2011 13:17:10          1
04/01/2011 05:30:30          4
04/01/2011 08:08:13          5
04/01/2011 14:42:24          3
04/01/2011 20:20:58          3
05/01/2011 17:29:24          2
05/01/2011 17:40:20          4
05/01/2011 18:32:56          2
06/01/2011 04:12:53          5
06/01/2011 08:59:18          2
06/01/2011 09:04:26          3
06/01/2011 10:14:20          1
06/01/2011 14:22:54          1
06/01/2011 19:39:04          1
08/01/2011 14:44:18          5
08/01/2011 21:38:04          5
11/01/2011 04:56:05          4
11/01/2011 18:52:29          2
11/01/2011 23:57:30          4
13/01/2011 07:24:22          3
20 rows selected.I came up to that query :select
        v.*,
        case
                when unq_l3d is null then -1
                else trunc(unq_today/unq_l3d,2)
        end ratio
from (
        select distinct trcdt, unq_today, unq_l3d
        from (
                select
                trcdt,
                count(user_id)
                over (
                        order by trcdt
                        range between numtodsinterval(1,'DAY') preceding and current row
                ) unq_today,
                count(user_id)
                over (
                        order by trcdt
                        range between numtodsinterval(3,'DAY') preceding and current row
                ) unq_l3d
                from (
                        select distinct trunc(visit_date) trcdt, user_id from t
) v
order by trcdtWith my sample data, it gives me :TRCDT                UNQ_TODAY    UNQ_L3D RATIO
03/01/2011 00:00:00          1          1  1.00
04/01/2011 00:00:00          4          4  1.00
05/01/2011 00:00:00          5          6  0.83
06/01/2011 00:00:00          6         10  0.60
08/01/2011 00:00:00          1          7  0.14
11/01/2011 00:00:00          2          3  0.66
13/01/2011 00:00:00          1          3  0.33
7 rows selected.where :
- UNQ_TODAY is the number of distinct user_id in the day
- UNQ_L3D is the number of distinct user_id in the last 3 days
- RATIO is UNQ_TODAY divided by UNQ_L3D +(when UNQ_L3D is not zero)+
It seems quite correct, but you would have to modify the query to fit to your needs and double-check the results !
Just noticed that my query is all wrong*... must have been missing coffeine, or sleep.... but I'm still trying !
Edited by: Nicosa on Jan 13, 2011 5:29 PM