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

By:   |   Updated: 2022-04-04   |   Comments (2)   |   Related: More > Data Types


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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 msdb.dbo.sysssispackages
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 msdb.dbo.sysssispackages
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 msdb.dbo.sysssispackages
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.

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

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Article Last Updated: 2022-04-04

Comments For This Article




Wednesday, December 26, 2012 - 2:24:33 PM - Rodney Back To Top (21139)

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 (18269)
Greg, Nice tip. Helped me out :-) John














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