SQL Server making rows into columns

Question

I\'m trying to take three tables that I have and show the data in a way the user asked me to do it. The tables look like this. (I should add that I am using MS SQL Server)

Answer 1

There are several ways that you can get the result, including using the PIVOT function.

You can use an aggregate function with a CASE expression:

select t1.aid, t1.status, t1.[group],
  max(case when t2.traitname = 'trait1' then t3.trait end) trait1,
  max(case when t2.traitname = 'trait2' then t3.trait end) trait2,
  max(case when t2.traitname = 'trait3' then t3.trait end) trait3
from table1 t1
inner join table3 t3
  on t1.aid = t3.aid
inner join table2 t2
  on t3.atid = t2.atid
group by t1.aid, t1.status, t1.[group];

See SQL Fiddle with Demo

The PIVOT function requires an aggregate function this is why you would need to use either the MIN or MAX function (since you have a string value).

If you have a limited number of traitnames then you could hard-code the query:

select aid, status, [group],
  trait1, trait2, trait3
from
(
  select t1.aid,
    t1.status,
    t1.[group],
    t2.traitname,
    t3.trait
  from table1 t1
  inner join table3 t3
    on t1.aid = t3.aid
  inner join table2 t2
    on t3.atid = t2.atid
) d
pivot
(
  max(trait)
  for traitname in (trait1, trait2, trait3)
) piv;

See SQL Fiddle with Demo.

If you have an unknown number of values, then you will want to look at using dynamic SQL to get the final result:

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

select @cols = STUFF((SELECT distinct ',' + QUOTENAME(traitname) 
                    from Table2
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT aid, status, [group],' + @cols + ' 
            from 
            (
              select t1.aid,
                t1.status,
                t1.[group],
                t2.traitname,
                t3.trait
              from table1 t1
              inner join table3 t3
                on t1.aid = t3.aid
              inner join table2 t2
                on t3.atid = t2.atid
            ) x
            pivot 
            (
                max(trait)
                for traitname in (' + @cols + ')
            ) p '

execute sp_executesql @query;

See SQL Fiddle with Demo