create table #Month ( [month] varchar(32))

insert into #month ([month])
select '1' [Month]
union all
select '2' [Month]
union all
select '3' [Month]
union all
select '4' [Month]
union all
select '5' [Month]


-- drop table #report
create table #report (id int identity(1,1) not null, salesperson int)

select 'alter table #report add [' + [month] + '] decimal(19,2) default 0' from #month
/*
alter table #report add [1] decimal(19,2) default 0
alter table #report add [2] decimal(19,2) default 0
alter table #report add [3] decimal(19,2) default 0
alter table #report add [4] decimal(19,2) default 0
alter table #report add [5] decimal(19,2) default 0
*/
-- drop table #invoices
create table #invoices (invoiceid int, invoicedate datetime, invoicetotal decimal(19,2), salesperson int, clientid int) 

insert into #invoices (invoiceid, invoicedate, invoicetotal, salesperson, clientid)
select 1, cast('2008-1-15' as datetime), 200, 1, 1
union all
select 1, cast('2008-2-15' as datetime), 100, 1, 1
union all
select 1, cast('2008-3-15' as datetime), 150, 1, 1

-- all salespersons you want
insert into #report (salesperson)
select distinct salesperson
from #invoices
where clientid = 1

select 'update r set [' + cast(datepart(month, invoicedate) as varchar(32)) + '] = ''' + cast(sum(invoicetotal) as varchar(32)) + ''' from #report r where salesperson = ' + cast(i.salesperson as varchar(32))
from #invoices i
where i.salesperson in (select salesperson from #invoices)
group by i.salesperson, datepart(month, i.invoicedate)
/*
update r set [1] = '200.00' from #report r where salesperson = 1
update r set [2] = '100.00' from #report r where salesperson = 1
update r set [3] = '150.00' from #report r where salesperson = 1
*/
select * from #report

truncate table #invoices

insert into #invoices (invoiceid, invoicedate, invoicetotal, salesperson, clientid)
select 1, cast('2008-1-15' as datetime), 200, 1, 1
union all
select 1, cast('2008-2-15' as datetime), 100, 1, 1
union all
select 1, cast('2008-3-15' as datetime), 150, 1, 1
union all
select 2, cast('2008-1-15' as datetime), 1200, 2, 1
union all
select 2, cast('2008-2-15' as datetime), 1100, 2, 1
union all
select 2, cast('2008-3-15' as datetime), 1150, 2, 1


select salespersons.salesperson, #month.[month], sum(i.invoicetotal) totaal
from #month, (select distinct salesperson
from #invoices) salespersons, #invoices i
where i.salesperson = salespersons.salesperson
and #month.[month] = datepart(month, i.invoicedate)
group by salespersons.salesperson, #month.[month]