Database size versus table data size

Question

I ran the below query that queries all tables in the database and the total size for reserved space is 17GB. The database size is 294GB. Why is there such a big difference in size. I would expect the database to be a little bigger but not 277GB bigger.
DECLARE @TableName VARCHAR(100)    --For storing values in the cursor
--Cursor to get the name of all user tables from the sysobjects listing
DECLARE tableCursor CURSOR FOR  
select [name] from dbo.sysobjects  where  OBJECTPROPERTY(id, N'IsUserTable') = 1 FOR READ ONLY
--A procedure level temp table to store the results
CREATE TABLE #TempTable (     tableName varchar(100),     numberofRows varchar(100),     reservedSize varchar(50),     dataSize varchar(50),     indexSize varchar(50),    
unusedSize varchar(50) )
--Open the cursor
OPEN tableCursor
--Get the first table name from the cursor
FETCH NEXT FROM tableCursor INTO @TableName
--Loop until the cursor was not able to fetch
WHILE (@@Fetch_Status >= 0) BEGIN     
--Dump the results of the sp_spaceused query to the temp table     
INSERT  #TempTable         
EXEC sp_spaceused @TableName     
--Get the next table name     
FETCH NEXT FROM tableCursor INTO @TableName END
--Get rid of the cursor
CLOSE tableCursor
DEALLOCATE tableCursor
--Select all records so we can use the reults
SELECT *  FROM #TempTable
order by 2
--Final cleanup!
DROP TABLE #TempTable
Alan

Answer 1

Hi anaylor,
According to your description, the database size is larger than sum of tables sizes. There could be a number of reasons , for example,
• There may have the large transaction, or a lot of data in the database but it has been removed in some process.
• Indexes/constraints are being stored in other files.
•Last database cleanup (including table deletion, record deletion) did not affect any disk reclamation.
•The initial size of the database is large.
• Have you calculate unused spaces? Databases usually trade space for speeding and allocating huge amounts of disk space ahead of time, to avoid allocation at transaction time. Space freed by delete may be reused or not due to speed reasons.
Hope it can help.
Regards,
Sofiya Li
Sofiya Li
TechNet Community Support