SQL Server query join several tables - sql

Question

I have a query that I don't think should be that hard to make, however, I've spent a lot of time on it now and still can't get it the way I want, so I hope someone here can help me.
Basically, I need to create a report that will give a value for each month, for each area. However, not all areas deliver data each month; in that case the view should return NULL for that month and area. So, the view need to look something like this:
Month Area Value
2012-08-01 Area1 2
2012-08-01 Area2 3
2012-09-01 Area1 3
2012-09-01 Area2 NULL
My data table looks something like this
Date Area Value
2012-08-01 Area1 2
2012-08-01 Area2 3
2012-09-01 Area1 3 -- Notice that Area2 is not present for September here
I have a table with all the available areas
Furthermore, I have created a table-valued function that returns all dates from a given date until now.
For example this statement
SELECT * FROM Periods_Months('2012-01-01')
would return 8 records like:
DateValue Year Month YearMonth
2012-01-01 00:00:00.000 2012 1 20121
2012-02-01 00:00:00.000 2012 2 20122
2012-03-01 00:00:00.000 2012 3 20123
2012-04-01 00:00:00.000 2012 4 20124
2012-05-01 00:00:00.000 2012 5 20125
2012-06-01 00:00:00.000 2012 6 20126
2012-07-01 00:00:00.000 2012 7 20127
2012-08-01 00:00:00.000 2012 8 20128
Based on the suggestions, my query now looks like this:
WITH months AS (
SELECT DateValue, YearMonth FROM Periods_Months('2011-01-01')
)
select m.DateValue
,CAST(DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,m.DateValue)+1,0)) AS Date) AS DateReported -- Get last day in month
,ResponseTime AS Value
,g.ExternalId
from GISDB.dbo.GisObjects g
CROSS JOIN months m
LEFT OUTER JOIN
( -- SELECT data from data table, grouped by area and month
SELECT dbo.YearMonth(CloseDate) AS YearMonth
,MAX(CloseDate) AS LastDate
,GisObjectId
,SUM(DATEDIFF(HH,RegDate,CloseDate)) AS ResponseTime -- calculate response time between start and end data (the value we need)
FROM DataTable
WHERE CloseDate IS NOT NULL
AND GisObjectId IS NOT NULL
GROUP BY GisObjectId, dbo.YearMonth(CloseDate) -- group by area and month
) c
ON g.ObjectId = c.GisObjectId AND c.YearMonth = m.YearMonth
WHERE g.CompanyId = 3 AND g.ObjectTypeId = 1 -- reduce the GIS objects that we compare to
ORDER BY m.DateValue, g.ObjectId
But the result is this (Value is always NULL):
DateValue DateReported Value ExternalId
2011-01-01 00:00:00.000 31-01-2011 NULL 9994
2011-01-01 00:00:00.000 31-01-2011 NULL 9993
2011-01-01 00:00:00.000 31-01-2011 NULL 9992
2011-01-01 00:00:00.000 31-01-2011 NULL 9991
2011-01-01 00:00:00.000 31-01-2011 NULL 2339
2011-01-01 00:00:00.000 31-01-2011 NULL 2338
2011-01-01 00:00:00.000 31-01-2011 NULL 2337
2011-01-01 00:00:00.000 31-01-2011 NULL 2336
2011-01-01 00:00:00.000 31-01-2011 NULL 2335
2011-01-01 00:00:00.000 31-01-2011 NULL 2334
2011-01-01 00:00:00.000 31-01-2011 NULL 2327
2011-01-01 00:00:00.000 31-01-2011 NULL 2326
2011-01-01 00:00:00.000 31-01-2011 NULL 2325
2011-01-01 00:00:00.000 31-01-2011 NULL 2324
2011-01-01 00:00:00.000 31-01-2011 NULL 2323
2011-01-01 00:00:00.000 31-01-2011 NULL 2322
etc.

Answer 1

I suppose you have a table with all your areas, which I call area_table.
WITH month_table AS (
SELECT dateValue FROM Periods_Months('2012-01-01')
)
select * from area_table
CROSS JOIN month_table
LEFT OUTER JOIN myValueTable
ON area_table.name = myValueTable.area
AND myValueTable.date = left(convert(varchar(30),month_table.dateValue,120),10)
ORDER BY myValueTable.Month, myValueTable.area

Answer 2

Suppose Areas is your table for all available areas, t - is your data table:
SELECT pm.dateValue,Ar.Area, t.value
FROM Periods_Months('2012-01-01') pm, Areas ar
left join t on (pm.dateValue=t.Date) and (ar.Area=t.Area)
order by pm.DateValue,ar.Area