SQL Server 2008 - How can I find the size (disk usage ) of a column in a table

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clinty

1182 posts

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#136237 20-Nov-2013 08:40

Hi,

Have a client whose SQL Server 2008 (Express) DB is very close to the 10GB hard limit. Upgrading to Full SQL Server is not an option.

I have told them we need to remove some data, and that it is likely that the photos that are stored with each contact are the issue. However they refuse to remove data unless I can prove that will resolve the issue (and even then I am not sure if they will do it)

I have confirmed with SSMS that the table containing the photos is 9.8GB but as it also holds all the other relevant contact data I can't prove it is the photos.

This is a commercial program so I can't alter any of the DB tables etc.

Is there an SQL command I can use to show the total size (MB,GB) of all the data stored in a column in a table so I can prove it is the photos?

cheers
Clint

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Inphinity

2780 posts

Uber Geek

#937697 20-Nov-2013 08:46

select sum(datalength(column)) from table

TwoSeven

1624 posts

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Subscriber

#937803 20-Nov-2013 11:32

Its not really a simple answer.

SQL Server stores data in 8K data pages, there are 8 pages to an extent (64kb) and 16 extents to a megabyte. A row in a page cannot be bigger than the page. There are three types of allocation unit, IN_ROW_DATA (normal stuff), LOB_DATA (your images, text etc,) and your ROW_OVERFLOW_DATA (varchar, varbinary etc.). If the data in a column in a data row (IN_ROW_DATA) contains more than 8K it will be moved to the ROW_OVERFLOW_DATA allocation unit. LOB data such as your images is ok.

To get the size of the database on disk SELECT used_page_count /128.0 FROM sys.dm_db_partition_stats will give you the size in megabytes.

To determine the allocation units and sizes used in each,

SELECT obj.name, alloc.type_desc, alloc.total_pages, alloc.used_pages, alloc.data_pages
FROM sys.allocation_units as alloc
JOIN sys.partitions as part on alloc.containter_id = part.partition_id
JOIN sys.objects as obj ON part.object_id = obj.object_id
WHERE obj.name = 'mytable'

This will give you the number of pages used in the LOB_DATA allocation unit which you can use to calculate the size on disk. It will also allow you to see the size of any large data fields you have that are moved to the ROW_OVERFLOW_DATA allocation unit.

Hope that provides some useful information regarding the issue.

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