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 understand what is the purpose of including the N before inserting any strings into the table.

INSERT INTO Personnel.Employees
VALUES(N'29730', N'Philippe', N'Horsford', 20.05, 1),

What purpose does this ‘N’ prefix serve, and when should it be used?

Answer 1

It’s declaring the string as nvarchar data type, rather than varchar

You may have seen Transact-SQL code that passes strings around using
an N prefix. This denotes that the subsequent string is in Unicode
(the N actually stands for National language character set). Which
means that you are passing an NCHAR, NVARCHAR or NTEXT value, as
opposed to CHAR, VARCHAR or TEXT.

To quote from Microsoft:

Prefix Unicode character string constants with the letter N. Without
the N prefix, the string is converted to the default code page of the
database. This default code page may not recognize certain characters.

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If you want to know the difference between these two data types, see this SO post:

What is the difference between varchar and nvarchar?