The 'N' in the where clause of SQL

Question

I saw this query somewhere -

SELECT *
FROM HR.Employees
WHERE country <> N'JAP';

What does that "N" mean ? I am not sure if this is valid only for SQL server.

Answer 1

The N stands for "National Character" and it means that the content of the string is Unicode.

You should be using Unicode (nchar/nvarchar) whenever you might come across proper names or other entities that can contain characters outside of the default ASCII character set. If you don't surround such strings with the N prefix, you will lose data. For example:

SELECT N'ук ферт хер', 'ук ферт хер';

Results:

-----------        -----------
ук ферт хер        ?? ???? ???

You should also be sure to use the N prefix in your WHERE or other clauses against n(var)char columns. When you don't use the N prefix, you could suffer serious performance issues due to implicit conversion.