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How to get length of Text, NText and Image columns in SQL Server


By:   |   Read Comments (4)   |   Related Tips: More > Data Types

Problem

There is sometimes a need to figure out the maximum space that is being used by a particular column in your database. You would initially think that the LEN() function would allow you to do this, but this function does not work on Text, NText or Image data types, so how do you figure out the length of a value in a column that has one of these data types?

Solution

In addition to the LEN() function, SQL Server also has a DATALENGTH() function. This function can be used on all data types in your table.

Here is an example of running these commands on an IMAGE data type using the LEN() function:

SELECT name, LEN(packagedata) 
FROM dbo.sysdtspackages
invalid argument error

Here is an example of running these commands on an IMAGE data type using the DATALENGTH() function:

SELECT name, DATALENGTH(packagedata) 
FROM dbo.sysdtspackages
data length output

If you wanted to find out the maximum length used for all of your records you could issue a command such as the following:

SELECT TOP 1 name, DATALENGTH(packagedata) 
FROM dbo.sysdtspackages 
ORDER BY 2 DESC
data length output

That's all there is to it. Another little function that you probably won't use often, but this is helpful to know it is there when you do need to use it.

Next Steps


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MSSQLTips author Greg Robidoux Greg Robidoux is the President of Edgewood Solutions and a co-founder of MSSQLTips.com.

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Wednesday, December 26, 2012 - 2:24:33 PM - Rodney Back To Top

It is important to note that DATALENGTH returns the number of BYTES used to store the string INCLUDING any ending whitespace, while the LEN function returns the number of CHARACTERS in a string EXCLUDING any ending whitespace.

For example, if you insert the value 'TEST' into an NVARCHAR field, the LEN function returns 4 while the DATALENGTH function returns 8 (each character in an NVARCHAR field requires two bytes of storage).  If you instead inserted the value 'TEST   ' (with three spaces at the end of the string) the LEN function would still return 4 while the DATALENGTH function returns 14 (8 bytes for TEST plus 6 bytes for the three trailing spaces).  Granted you still can't use the LEN function on large data types, but you should keep this difference in mind if you are planning to use the value in any string manipulations or character space calculations.


Friday, June 29, 2012 - 1:09:05 PM - John Back To Top

Greg,

 

Nice tip. Helped me out :-)

 

John


Friday, April 11, 2008 - 9:55:00 AM - admin Back To Top

Shaileshk,

Thank you.  That is certainly one approach.

Thank you,
The MSSQLTips.com Team


Friday, April 11, 2008 - 1:43:11 AM - shaileshk Back To Top

if you want to remove duplicate records with ntext,text and image datatype .please do the step as given into the link

http://www.codegroups.com/blog/index.php/deleting-duplicate-records-from-table-with-text-ntext-or-image-data-type/

I hope this is help !

Regards,
Shaileshk

 


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