Question

Given this data:

Name       Property   Value
---------- ---------- ----------
Bob        Hair       Red       
Bob        Eyes       Blue      
Fred       Hair       Brown     
Fred       Height     Tall      

what SQL would be required to produce these results?

Property   Bob        Fred
---------- ---------- ----------
Hair       Red        Brown     
Eyes       Blue             
Height                Tall     

I’m using SQL Server 2008, but a generic solution would be nice.

Answer 1

You did not specify what RDBMS you are using but this is a pivot. You can use an aggregate function and a CASE expression in all databases:

select property,
  max(case when name='Bob' then value else '' end) Bob,
  max(case when name='Fred' then value else '' end) Fred
from yourtable
group by property

See SQL Fiddle with Demo

If you are using a database that has a PIVOT function (SQL Server 2005+/Oracle 11g+), then your code will be similar to this:

select *
from
(
  select property, name, value
  from yourtable
) src
pivot
(
  max(value)
  for name in (Bob, Fred)
) piv

See SQL Fiddle with Demo

The above queries work great, if you know the name values ahead of time, but if you don’t then you will want to use dynamic sql:

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

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

set @query = 'SELECT property,' + @cols + ' from 
             (
                select property, name, value
                from yourtable
            ) x
            pivot 
            (
                max(value)
                for name in (' + @cols + ')
            ) p '

execute(@query)

See SQL Fiddle with Demo

All three will produce the same result:

| PROPERTY |  BOB |  FRED |
---------------------------
|     Eyes | Blue |       |
|     Hair |  Red | Brown |
|   Height |      |  Tall |