--The first CTE gets the content as a varbinary(max)
--as well as the other important columns for all reports,
--data sources and shared datasets.
WITH ItemContentBinaries AS
(
  SELECT
     ItemID,Name,[Type]
    ,CASE Type
       WHEN 2 THEN 'Report'
       WHEN 5 THEN 'Data Source'
       WHEN 7 THEN 'Report Part'
       WHEN 8 THEN 'Shared Dataset'
       ELSE 'Other'
     END AS TypeDescription
    ,CONVERT(varbinary(max),Content) AS Content
  FROM ReportServer.dbo.Catalog
  WHERE Type IN (2,5,7,8)
),
--The second CTE strips off the BOM if it exists...
ItemContentNoBOM AS
(
  SELECT
     ItemID,Name,[Type],TypeDescription
    ,CASE
       WHEN LEFT(Content,3) = 0xEFBBBF
         THEN CONVERT(varbinary(max),SUBSTRING(Content,4,LEN(Content)))
       ELSE
         Content
     END AS Content
  FROM ItemContentBinaries
)
--The outer query gets the content in its varbinary, varchar and xml representations...
SELECT
   ItemID,Name,[Type],TypeDescription
  ,Content --varbinary
  ,CONVERT(varchar(max),Content) AS ContentVarchar --varchar
  ,CONVERT(xml,Content) AS ContentXML --xml
FROM ItemContentNoBOM

--http://bretstateham.com/extracting-ssrs-report-rdl-xml-from-the-reportserver-database/