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  SQL Server Tips by Gama and Naughter



Nchar stores fixed length Unicode data. The data is padded with spaces on the right as this example shows:


DECLARE @b nchar(10)

SET @b='abc'

select DATALENGTH(@b), LEN(@b)



20    3



Each Unicode character takes two bytes and DATALENGTH returns the length in terms of bytes, therefore twenty. LEN returns the number of characters and it should be three because 'abc' is only three characters.


Note: For ASCII data types, LEN and DATALENGTH return the same value, unless the data has trailing spaces, which are not counted. This is an important detail that results in subtle bugs.


The above book excerpt is from:

Super SQL Server Systems
Turbocharge Database Performance with C++ External Procedures

ISBN: 0-9761573-2-2
Joseph Gama, P. J. Naughter


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