How to find largest objects in a SQL Server database?

In SQL Server 2008, you can also just run the standard report Disk Usage by Top Tables. This can be found by right clicking the DB, selecting Reports->Standard Reports and selecting the report you want.

This query help to find largest table in you are connection.

SELECT  TOP 1 OBJECT_NAME(OBJECT_ID) TableName, st.row_count
FROM sys.dm_db_partition_stats st
WHERE index_id < 2
ORDER BY st.row_count DESC

I've been using this SQL script (which I got from someone, somewhere - can't reconstruct who it came from) for ages and it's helped me quite a bit understanding and determining the size of indices and tables:

SELECT 
    t.name AS TableName,
    i.name as indexName,
    sum(p.rows) as RowCounts,
    sum(a.total_pages) as TotalPages, 
    sum(a.used_pages) as UsedPages, 
    sum(a.data_pages) as DataPages,
    (sum(a.total_pages) * 8) / 1024 as TotalSpaceMB, 
    (sum(a.used_pages) * 8) / 1024 as UsedSpaceMB, 
    (sum(a.data_pages) * 8) / 1024 as DataSpaceMB
FROM 
    sys.tables t
INNER JOIN      
    sys.indexes i ON t.object_id = i.object_id
INNER JOIN 
    sys.partitions p ON i.object_id = p.object_id AND i.index_id = p.index_id
INNER JOIN 
    sys.allocation_units a ON p.partition_id = a.container_id
WHERE 
    t.name NOT LIKE 'dt%' AND
    i.object_id > 255 AND  
    i.index_id <= 1
GROUP BY 
    t.name, i.object_id, i.index_id, i.name 
ORDER BY 
    object_name(i.object_id) 

Of course, you can use another ordering criteria, e.g.

ORDER BY SUM(p.rows) DESC

to get the tables with the most rows, or

ORDER BY SUM(a.total_pages) DESC

to get the tables with the most pages (8K blocks) used.

You may also use the following code:

USE AdventureWork
GO
CREATE TABLE #GetLargest 
(
  table_name    sysname ,
  row_count     INT,
  reserved_size VARCHAR(50),
  data_size     VARCHAR(50),
  index_size    VARCHAR(50),
  unused_size   VARCHAR(50)
)

SET NOCOUNT ON

INSERT #GetLargest

EXEC sp_msforeachtable 'sp_spaceused ''?'''

SELECT 
  a.table_name,
  a.row_count,
  COUNT(*) AS col_count,
  a.data_size
  FROM #GetLargest a
     INNER JOIN information_schema.columns b
     ON a.table_name collate database_default
     = b.table_name collate database_default
       GROUP BY a.table_name, a.row_count, a.data_size
       ORDER BY CAST(REPLACE(a.data_size, ' KB', '') AS integer) DESC

DROP TABLE #GetLargest