Join tables with rows - sql

Question

I am trying to join three tables in SQL Server 2008 R2, where I want the items in the second table to be added as new column.
To explain in detail - I have 3 tables:
First table contains User Name and User ID
UserID UserName
1 Mike
2 John
3 George
Second Table is position ID's with Position Names
PositionID PositionName
1 RW
2 LW
3 DF
4 MDF
5 SS
6 CF
etc
Third table table contains their preferred positions where one user can have more than one
UserID PositionId
1 1
1 3
2 2
2 3
2 5
3 2
3 7
When I join these tables I want to get single row for every user with all the preferred positions like
UserID UserName PreferedPosition PreferedPosition2 PreferedPosition3
1 Mike RW LW
2 John CMF SS CF
3 George LW MDF
I don't know how to achieve this, any help would be appreciated.

Answer 1

If you have only a few numbers of positions, you can do it with PIVOT keyword
select
UserID,
UserName,
[1] as Position1,
[2] as Position2,
[3] as Position3
from
(
select
U.UserID, U.UserName, P.PositionName,
row_number() over (partition by U.UserID order by P.PositionName) as RowNum
from Positions_Users as PU
inner join Positions as P on P.PositionID = PU.PositionID
inner join Users as U on U.UserID = PU.UserID
) as P
pivot
(
min(P.PositionName)
for P.RowNum in ([1], [2], [3])
) as PIV
SQL FIDDLE
If, however, you want to have a dynamic number of columns, you have to use dynamic SQL, like this
declare #stmt nvarchar(max), #stmt_columns1 nvarchar(max), #stmt_columns2 nvarchar(max)
declare #Temp_Data table (RowNum nvarchar(max))
insert into #Temp_Data
select distinct row_number() over (partition by U.UserID order by P.PositionName) as RowNum
from Positions_Users as PU
inner join Positions as P on P.PositionID = PU.PositionID
inner join Users as U on U.UserID = PU.UserID
select #stmt_columns1 = stuff((select ', [' + RowNum + ']' from #Temp_Data for xml path(''), type).value('.', 'nvarchar(max)'), 1, 2, '')
select #stmt_columns2 = stuff((select ', [' + RowNum + '] as Position' + RowNum from #Temp_Data for xml path(''), type).value('.', 'nvarchar(max)'), 1, 2, '')
select #stmt = '
select
UserID,
UserName,' + #stmt_columns2 + '
from
(
select
U.UserID, U.UserName, P.PositionName,
row_number() over (partition by U.UserID order by P.PositionName) as RowNum
from Positions_Users as PU
inner join Positions as P on P.PositionID = PU.PositionID
inner join Users as U on U.UserID = PU.UserID
) as P
pivot
(
min(P.PositionName)
for P.RowNum in (' + #stmt_columns1 + ')
) as PIV'
exec sp_executesql #stmt = #stmt
SQL FIDDLE