Question

I’m sure this won’t be a difficult question for the hardcore SQL geeks, but I need some help. This is for SQL Server 2000 (inherited projects!).

I have a table of salary listings that look like this:

EmployeeID  |  EffectiveDate  | Salary
1           |   2/1/2011      | 500
1           |   6/1/2011      | 600
1           |   12/1/2011     | 650

I need to create a query that will output these salaries by month for a given year. So the output would be like

EmployeeID  | Jan | Feb | Mar | Apr | Apr | May | Jun | Jul | Aug | Sept | Oct | Nov | Dec
1           | 500 | 500 | 500 | 500 | 500 | 500 | 600 | 600 | 600 | 600  | 600 | 600 | 650

I know there must be a way to do this effectively with SQL, I just can’t seem to get it right. Obviously, I would be naming the month columns above with SQL such as
SELECT EmployeeID, ‘Jan’ AS Jan, ‘Feb’ AS Feb, etc but the rest of the statement is harder since I’m looking for ranges.

Answer 1

Since you are using SQL Server 2000 it does not have a PIVOT function, so you will have to replicate this using an aggregate function and a CASE statement. Similar to this:

select  employeeid,
  sum(case when DatePart(Month, EffectiveDate) = 1 then Salary end) as Jan,
  sum(case when DatePart(Month, EffectiveDate) = 2 then Salary end) as Feb,
  sum(case when DatePart(Month, EffectiveDate) = 3 then Salary end) as Mar,
  sum(case when DatePart(Month, EffectiveDate) = 4 then Salary end) as Apr,
  sum(case when DatePart(Month, EffectiveDate) = 5 then Salary end) as May,
  sum(case when DatePart(Month, EffectiveDate) = 6 then Salary end) as Jun,
  sum(case when DatePart(Month, EffectiveDate) = 7 then Salary end) as Jul,
  sum(case when DatePart(Month, EffectiveDate) = 8 then Salary end) as Aug,
  sum(case when DatePart(Month, EffectiveDate) = 9 then Salary end) as Sep,
  sum(case when DatePart(Month, EffectiveDate) = 10 then Salary end) as Oct,
  sum(case when DatePart(Month, EffectiveDate) = 11 then Salary end) as Nov,
  sum(case when DatePart(Month, EffectiveDate) = 12 then Salary end) as Dec
from  yourtable
group by employeeid

See SQL Fiddle with Demo

Edit, based on your comments above carrying over the value from one month to the next, here is a solution that might work for you.

declare @query as nvarchar(max) = '',
  @rowcount as int = 1,
  @pivotrow as int,
  @currentMonthSalary as int = 0,
  @priorMonthSalary as int = 0,
  @employeeid int 

select distinct effectivedate
into #colspivot
from yourtable

while @rowcount <= 12 -- loop thru each month
  begin

    set @pivotrow = (select top 1 datepart(month, effectivedate)
                        from #colspivot
                        order by datepart(month, effectivedate))

    select @currentMonthSalary = salary, @employeeid = EmployeeID
            from yourtable
            where datepart(month, effectivedate) = @pivotrow

    if @pivotrow = @rowcount
        begin
            insert into FinalData (employeeid, effectivemonth, salary)
            select @employeeid, cast(DateName(month, DateAdd(month, @pivotrow, 0) -1) as varchar(3)), @currentMonthSalary

            set @query = @query + ', sum(case when effectivemonth = ''' +  cast(DateName(month, DateAdd(month, @pivotrow, 0) -1) as varchar(3)) + ''' 
                                        then ' + cast(@currentMonthSalary as varchar(10)) + ' end) as '+ cast(DateName(month, DateAdd(month, @pivotrow, 0) -1) as varchar(3))

            delete from #colsPivot where datepart(month, effectivedate) = @pivotRow

            set @priorMonthSalary = @currentMonthSalary
        end
    else
        begin
            insert into FinalData (employeeid, effectivemonth, salary)
            select @employeeid, cast(DateName(month, DateAdd(month, @rowcount, 0) -1) as varchar(3)), @priorMonthSalary

            set @query = @query + ', sum(case when effectivemonth = ''' + cast(DateName(month, DateAdd(month, @rowcount, 0) -1) as varchar(3)) + '''  
                        then ' +  cast(@priorMonthSalary as varchar(10)) + ' end) as '+cast(DateName(month, DateAdd(month, @rowcount, 0) -1) as varchar(3))
        end

    if @rowcount <= 12
      set @rowcount = @rowcount + 1
  end

set @query = 'select employeeid '+ @query 
              + ' from FinalData group by employeeid;'

exec(@query) 

See SQL Fiddle with Demo. I created a new table FinalData to store the data for each month while I loop through creating the sql statement.