Oracle SQL -- Using A Date Function to improve a query - sql

Question

I have this query
--Retention by DOC,Users created >= Jan 1,2012--
Select
One.Date_Of_Concern,
Two.Users,
One.Retained,
Round(One.Retained/Two.Users,4) as Perc_Retained
From
(
Select
To_Date('2012-sep-09','yyyy-mon-dd')As Date_Of_Concern,
Count(P.Player_Id) As Retained
From Player P
Where
Trunc(P.Create_Dtime) >= To_Date('2012-Jan-01','yyyy-mon-dd')
And
(To_Date('2012-sep-09','yyyy-mon-dd')-Trunc(P.Init_Dtime))<=7
) One
Inner Join
(
Select
To_Date('2012-sep-09','yyyy-mon-dd')As Date_Of_Concern,
Count(P.Player_Id) As Users
From Player P
Where
Trunc(P.Create_Dtime) >= To_Date('2012-Jan-01','yyyy-mon-dd')
) Two On One.Date_Of_Concern = Two.Date_Of_Concern
Which Gives Me a Result of 1 Row:
Date_Of_Concern USERS RETAINED PERC_RETAINED
09-Sep-12 449773 78983 0.1756
I would like to improve this query by adding in some sort of date changing methodology. That way, I won't have to run the query each time for 09-sep-12, 10-sep-12, 11-sep-12, and so on. Instead, it will all show up in the same query, like this:
Date_Of_Concern USERS RETAINED PERC_RETAINED
09-Sep-12 449773 48783 0.1756
10-Sep-12 449773 46777 0.1600
11-Sep-12 440773 44852 0.1500
12-Sep-12 349773 42584 0.1400

Answer 1

Well, with the given information, i don't know if you have any table you can join and bring those dates. However, if you do not, you could try this:
We have to generate rows and reproduce the dates in a sequential form. But first, lets give a look at how to generate rows:
Generate 5 rows:
SELECT rownum
FROM dual
CONNECT BY LEVEL <= 5;
ROWNUM
----------
1
2
3
4
5
Now, applying this to reproduce a data source for your dates:
SELECT to_date('2012-sep-09','yyyy-mon-dd') + (rownum -1) as Date_Of_Concern
FROM dual
CONNECT BY LEVEL <= 5;
Date_Of_Concern
----------
2012-sep-09
2012-sep-10
2012-sep-11
2012-sep-12
2012-sep-13
Obviously you will need a start date. Additionally, the number 5 has to be replaced by the number of dates you need, it could be a date range like
SELECT to_date('2012-sep-09','yyyy-mon-dd') + (rownum -1) date
FROM dual
CONNECT BY LEVEL <= (to_date('2012-sep-20','yyyy-mon-dd') - to_date('2012-sep-09','yyyy-mon-dd'));
OK, now the final result would look like this:
SELECT both.Date_Of_Concern,
both.Retained,
both.Users,
Round(both.Retained/both.Users,4) as Perc_Retained
FROM (select Date_Of_Concern,
(Select Count(P.Player_Id) As Retained
From Player P
Where Trunc(P.Create_Dtime) >= To_Date('2012-Jan-01','yyyy-mon-dd')
And (Date_Of_Concern-Trunc(P.Init_Dtime))<=7) Retained,
(Select Count(P.Player_Id) As Users
From Player P
Where Trunc(P.Create_Dtime) >= To_Date('2012-Jan-01','yyyy-mon-dd')
) Users
from (SELECT to_date('2012-sep-09','yyyy-mon-dd') + (rownum -1) Date_Of_Concern,
FROM dual
CONNECT BY LEVEL <= 5)) both

Answer 2

I have a feeling your query can be simplified a lot. Here is an attempt to list day by day from the beginning of 2012. Depends what kind of range you are looking for.
SELECT date_of_concern
,Running_Total_Users AS Users
,Running_Total_Retained As Retained
,ROUND(Running_Total_Retained / Running_Total_Users, 4) AS Perc_Retained
FROM ( SELECT date_of_concern
,SUM(Users) OVER( ORDER BY date_of_concern
ROWS BETWEEN UNBOUNDED PRECEDING
AND CURRENT ROW ) AS Running_Total_Users
,SUM(Retained) OVER( ORDER BY date_of_concern
ROWS BETWEEN UNBOUNDED PRECEDING
AND CURRENT ROW ) AS Running_Total_Retained
FROM ( SELECT TRUNC(Create_Dtime) date_of_concern
,COUNT(Player_Id) Users
,SUM( CASE WHEN (TRUNC(Create_Dtime) - TRUNC(Init_Dtime)) <= 7 THEN 1 ELSE 0 END ) AS Retained
FROM player ON ( TRUNC(.Create_Dtime) >= TO_DATE('2012', 'YYYY') )
)
)
The inner most query is an attempt to re-write the posted query counting from day 1 (Jan 1 2012). Then the next wrapper is supposed to do running totals for each subsequent day. The final wrapper is to enable the Perc_Retained. Completed untested of course :)