What is the meaning of the prefix N in T-SQL statements and when should I use it?

Question

I have seen prefix N in some insert T-SQL queries. Many people have used N before inserting the value in a table.

I searched, but I was not able to unde

Answer 1

Let me tell you an annoying thing that happened with the N' prefix - I wasn't able to fix it for two days.

My database collation is SQL_Latin1_General_CP1_CI_AS.

It has a table with a column called MyCol1. It is an Nvarchar

This query fails to match Exact Value That Exists.

SELECT TOP 1 * FROM myTable1 WHERE  MyCol1 = 'ESKİ'  

// 0 result

using prefix N'' fixes it

SELECT TOP 1 * FROM myTable1 WHERE  MyCol1 = N'ESKİ'  

// 1 result - found!!!!

Why? Because latin1_general doesn't have big dotted İ that's why it fails I suppose.