Put N Unicode before variable in SQL Server?

Question

We usually use N for unicode string literals like this:

Select * 
From Customer 
Where Name = N'កខគ' --Unicode

Now I want to change it to be like this:

Declare @a varchar(Max)

Select * 
From Customer 
Where Name = N''+@a

At the second SQL statement it doesn't work at all. Any ideas? Thank you in advance.

Answer 1

The N is only used as a prefix to coerce unicode literals. If your @a variable is already one of the unicode types (e.g. NVARCHAR) then it's not necessary to convert or coerce it in any way.