TSQL Fill gaps in months and repeat values in column - tsql

Question

Started with TSQL last Wednesday...
I have the following data in tblStage1:
PROJECT USERNAME DATE PERCENTAGE
--------- ----------------- ------------ ----------------------
Project 1 DOMAIN\Chris.User 03/01/2013 0.25
Project 1 DOMAIN\Chris.User 05/01/2013 0.75
Project 1 DOMAIN\Chris.User 07/01/2013 1
Project 1 DOMAIN\John.User 02/01/2013 1
Project 1 DOMAIN\John.User 06/01/2013 0.5
I have the following data in tblRawData
PROJECT START_DATE END_DATE
---------- ----------- ----------
Project 1 01/01/2013 09/01/2013
I would like to get the following data out into tblStage2 (data points are bound by START_DATE and END_DATE):
PROJECT USERNAME DATE PERCENTAGE
--------- ----------------- ------------ ----------------------
Project 1 DOMAIN\Chris.User 01/01/2013 0
Project 1 DOMAIN\Chris.User 02/01/2013 0
Project 1 DOMAIN\Chris.User 03/01/2013 0.25
Project 1 DOMAIN\Chris.User 04/01/2013 0.25
Project 1 DOMAIN\Chris.User 05/01/2013 0.75
Project 1 DOMAIN\Chris.User 06/01/2013 0.75
Project 1 DOMAIN\Chris.User 07/01/2013 1
Project 1 DOMAIN\Chris.User 08/01/2013 1
Project 1 DOMAIN\Chris.User 09/01/2013 1
Project 1 DOMAIN\John.User 01/01/2013 0
Project 1 DOMAIN\John.User 02/01/2013 1
Project 1 DOMAIN\John.User 03/01/2013 1
Project 1 DOMAIN\John.User 04/01/2013 1
Project 1 DOMAIN\John.User 05/01/2013 1
Project 1 DOMAIN\John.User 06/01/2013 0.5
Project 1 DOMAIN\John.User 07/01/2013 0.5
Project 1 DOMAIN\John.User 08/01/2013 0.5
Project 1 DOMAIN\John.User 09/01/2013 0.5
I realize that there are a number of topics that relate to this subject such as this. I my case, I don't have any particular restrictions and I am looking for a clean routine that is relatively easy to understand.
I know there is a DateAdd function, but I haven't seen any INSERT INTO commands in the example statements. I am confused as to how one would iterate through the data set and create the interpolated values. I am still too green to understand the full context of the other examples and would greatly appreciate any help or clarification.
Edit Added additional information to the sample data for a better indication of my final goal. I will have multiple users in this data set. The USERNAME column is placed into the data set by the original source (a people picker on an InfoPath form). All "Percentages" are "0" until the first value is assigned then they retain that value until it is changed or the project reaches its end date. I hope this helps clarify!

Answer 1

It's not clear how USERNAME populated. I assume you have same USERNAME on project here. CTE below just build a DATE table, if you have your own date table, you can skip this part.
SQL Fiddle
DECLARE #ENDDate DATETIME
SELECT #ENDDate = MAX(END_DATE) FROM tblRawData
;WITH tblDate AS
( SELECT CAST(MIN(START_DATE) AS DATE) AS [date]
FROM tblRawData
UNION ALL
SELECT DATEADD(month,1,[DATE])
FROM tblDate
WHERE [DATE] < #ENDDate
)
SELECT
d.[date]
,r.[Project]
,UserName = (SELECT MAX(USERNAME) FROM tblStage1 ts WHERE r.PROJECT = ts.PROJECT)
,Percentage = (SELECT ISNULL(MAX(Percentage),0) FROM tblStage1 ts WHERE r.PROJECT = ts.PROJECT AND ts.[date] <= d.[date])
FROM tblDate d
INNER JOIN tblRawData r
ON d.[date] between r.[START_DATE] AND r.[END_DATE]
ORDER BY 2,1
OPTION (Maxrecursion 0)
EDIT: Just found out the date is increased by month. I update the CTE query. However, you need make sure you have all project start and end date at first day of the month.
EDIT
Base on your new sample date. the query became a little ugly now, however, it works. I can not think better solution right now.
New SQL Fiddler
DECLARE #ENDDate DATETIME
SELECT #ENDDate = MAX(END_DATE) FROM tblRawData
;WITH tblDate AS
( SELECT CAST(MIN(START_DATE) AS DATE) AS [date]
FROM tblRawData
UNION ALL
SELECT DATEADD(month,1,[DATE])
FROM tblDate
WHERE [DATE] < #ENDDate
)
,ProjectList AS (
SELECT Project,UserName
FROM tblStage1
GROUP BY Project,UserName
)
,cte AS (
SELECT
d.[date]
,r.[Project]
,UserName = pl.Username
,CloseDate = (SELECT MAX(ts.[date]) FROM tblStage1 ts WHERE r.PROJECT = ts.PROJECT AND ts.UserName = pl.UserName AND ts.[date] <= d.[date])
FROM tblDate d
INNER JOIN tblRawData r
ON d.[date] between r.[START_DATE] AND r.[END_DATE]
CROSS APPLY ProjectList pl
)
SELECT cte.[date],cte.project,cte.UserName,ISNULL(t.[PERCENTAGE],0) AS PERCENTAGE
FROM cte
LEFT JOIN tblStage1 t
ON cte.PROJECT = t.PROJECT
AND cte.UserName = t.UserName
AND cte.CloseDate = t.[Date]
ORDER BY 2,3,1

Answer 2

You could do this with the APPLY operator as well...
WITH DateList (Project, MonthStart) AS
(
SELECT
project
, Start_Date
FROM
tblRawData
UNION ALL
SELECT
dl.Project
, DATEADD(MONTH, 1, dl.MonthStart)
FROM
DateList dl
JOIN
tblRawData r
ON
r.Project = dl.Project
AND
dl.MonthStart < r.End_Date
)
SELECT
dl.Project
, lastUser.UserName
, dl.monthstart [Date]
, ISNULL(pct.Percentage, 0) Percentage
FROM
DateList dl
CROSS APPLY
(
SELECT
TOP 1
USERNAME
FROM
tblStage1 t1
WHERE
t1.Project = dl.Project
ORDER BY
t1.Date DESC
) lastUser
OUTER APPLY
(
SELECT
TOP 1
Percentage
FROM
tblStage1 t2
WHERE
t2.Project = dl.Project
AND
t2.Date <= dl.MonthStart
ORDER BY
t2.Date DESC
) pct

Answer 3

A really easy way would be to create a temp table with the month values of each month you need then doing a left join on that table.
Out of curiosity - why is August 1 instead of 0?