sql server - dynamic pivot and calculated columns

Question

I am looking for help generating a table with dynamic columns and calculated values in SQL Server from the following (abbreviated) source tables:

Assignments Source Table

Name     StartDate     EndDate      Value     Factor
Jim      2013-08-01    2013-09-06   200.0     0.5
Bob      2013-07-27    2013-11-01   140.0     1.0
Alice    2013-08-29    2014-03-22   200.0     0.8
Jim      2013-08-20    2013-09-01   250.0     0.5

Reporting Weeks Source Table

WeekEndDate
2013-08-18
2013-08-25
2013-09-01
2013-09-08

Desired Results Table

Name     StartDate     EndDate      Value     Factor  2013-08-18  2013-08-25  2013-09-01 2013-09-08
Jim      2013-08-01    2013-09-06   200.0     0.5     100.0       100.0       100.0      0.0
Bob      2013-07-27    2013-11-01   140.0     1.0     140.0       140.0       140.0      140.0
Alice    2013-08-29    2014-03-22   200.0     0.8     0.0         0.0         160.0      160.0
Jim      2013-08-20    2013-09-01   250.0     0.5     0.0         125.0       125.0      0.0

Basically, I need to turn the reporting rows table into columns and then calculate a value where the pivoted column date (Reporting Weeks/WeekEndDate) is between the StartDate and EndDate. If the date is outside that range the value should be set to zero. The "Reporting Weeks" table can vary over time, and may be generated from another query. The StartDate and EndDate will usually not match the WeekEndDate. I have been going over a lot of questions/answers around dynamic sql pivots, but haven't found anything that I can adapt to fit the need given my limited background in this area.

Answer 1

Before tackling the dynamic SQL version of this, I would first write the query as a static version using your limited dates. In order to get the result, I would calculate the value that you need in a subquery and then pivot on the weekenddates.

The basic syntax if you have a limited number of values would be:

select name, startdate, enddate,
  value, factor,
  coalesce([2013-08-18], 0) [2013-08-18], 
  coalesce([2013-08-25], 0) [2013-08-25],
  coalesce([2013-09-01], 0) [2013-09-01], 
  coalesce([2013-09-08], 0) [2013-09-08]
from
(
  select a.name,
    a.startdate,
    a.enddate,
    a.value,
    a.factor,
    convert(varchar(10), r.weekenddate, 120) weekenddate,
    amt = a.value * a.factor
  from assignments a
  inner join reportingweeks r
    on r.weekenddate >= a.startdate
    and r.weekenddate <= a.enddate
) d
pivot
(
  sum(amt)
  for weekenddate in ([2013-08-18], [2013-08-25], [2013-09-01], 
                      [2013-09-08])
) piv;

See SQL Fiddle with Demo. Once you have the correct logic, then you can convert the query into dynamic SQL:

DECLARE @cols AS NVARCHAR(MAX),
    @colsNull AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX)

select @cols = STUFF((SELECT ',' + QUOTENAME(dt) 
                    from
                    (
                      select convert(varchar(10), weekenddate, 120) dt
                      from reportingweeks
                    ) d
                    group by dt
                    order by dt
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

select @colsNull = STUFF((SELECT ', coalesce(' + QUOTENAME(dt)+', 0) as '+QUOTENAME(dt)
                    from
                    (
                      select convert(varchar(10), weekenddate, 120) dt
                      from reportingweeks
                    ) d
                    group by dt
                    order by dt
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT name, startdate, enddate,
                value, factor, ' + @colsNull + ' 
            from 
            (
              select a.name,
                a.startdate,
                a.enddate,
                a.value,
                a.factor,
                convert(varchar(10), r.weekenddate, 120) weekenddate,
                amt = a.value * a.factor
              from assignments a
              inner join reportingweeks r
                on r.weekenddate >= a.startdate
                and r.weekenddate <= a.enddate
            ) x
            pivot 
            (
                sum(amt)
                for weekenddate in (' + @cols + ')
            ) p '

execute sp_executesql @query;

See SQL Fiddle with Demo. Both will give a result:

|  NAME |  STARTDATE |    ENDDATE | VALUE | FACTOR | 2013-08-18 | 2013-08-25 | 2013-09-01 | 2013-09-08 |
|-------|------------|------------|-------|--------|------------|------------|------------|------------|
| Alice | 2013-08-29 | 2014-03-22 |   200 |    0.8 |          0 |          0 |        160 |        160 |
|   Bob | 2013-07-27 | 2013-11-01 |   140 |      1 |        140 |        140 |        140 |        140 |
|   Jim | 2013-08-01 | 2013-09-06 |   200 |    0.5 |        100 |        100 |        100 |          0 |
|   Jim | 2013-08-20 | 2013-09-01 |   250 |    0.5 |          0 |        125 |        125 |          0 |