Scrip to find Schema level size information in SQL Server

--Script to know number of tables, row count, data size, index size, used size
BEGIN TRY
 SELECT
  --(row_number() over(order by a3.name, a2.name))%2 as l1,
  a3.NAME AS [schemaname]
  ,count(a2.NAME) AS NumberOftables
  ,sum(a1.rows) AS row_count
  ,sum((a1.reserved + ISNULL(a4.reserved, 0)) * 8) AS reserved
  ,sum(a1.data * 8) AS data
  ,sum((
    CASE 
     WHEN (a1.used + ISNULL(a4.used, 0)) > a1.data
      THEN (a1.used + ISNULL(a4.used, 0)) - a1.data
     ELSE 0
     END
    ) * 8) AS index_size
  ,sum((
    CASE 
     WHEN (a1.reserved + ISNULL(a4.reserved, 0)) > a1.used
      THEN (a1.reserved + ISNULL(a4.reserved, 0)) - a1.used
     ELSE 0
     END
    ) * 8) AS unused
 FROM (
  SELECT ps.object_id
   ,SUM(CASE 
     WHEN (ps.index_id < 2)
      THEN row_count
     ELSE 0
     END) AS [rows]
   ,SUM(ps.reserved_page_count) AS reserved
   ,SUM(CASE 
     WHEN (ps.index_id < 2)
      THEN (ps.in_row_data_page_count + ps.lob_used_page_count + ps.row_overflow_used_page_count)
     ELSE (ps.lob_used_page_count + ps.row_overflow_used_page_count)
     END) AS data
   ,SUM(ps.used_page_count) AS used
  FROM sys.dm_db_partition_stats ps
  GROUP BY ps.object_id
  ) AS a1
 LEFT JOIN (
  SELECT it.parent_id
   ,SUM(ps.reserved_page_count) AS reserved
   ,SUM(ps.used_page_count) AS used
  FROM sys.dm_db_partition_stats ps
  INNER JOIN sys.internal_tables it ON (it.object_id = ps.object_id)
  WHERE it.internal_type IN (
    202
    ,204
    )
  GROUP BY it.parent_id
  ) AS a4 ON (a4.parent_id = a1.object_id)
 INNER JOIN sys.all_objects a2 ON (a1.object_id = a2.object_id)
 INNER JOIN sys.schemas a3 ON (a2.schema_id = a3.schema_id)
 WHERE a2.type <> 'S'
  AND a2.type <> 'IT'
 GROUP BY a3.NAME
 ORDER BY a3.NAME
END TRY

BEGIN CATCH
 SELECT - 100 AS l1
  ,1 AS schemaname
  ,ERROR_NUMBER() AS tablename
  ,ERROR_SEVERITY() AS row_count
  ,ERROR_STATE() AS reserved
  ,ERROR_MESSAGE() AS data
  ,1 AS index_size
  ,1 AS unused
END CATCH