difference between set @flag =1 and set @@flag = 1

Question

Hi What is the difference between

set @flag=1 and set @@flag = 1 in SQL Server?

Thank you

Answer 1

Nothing. Some in-built functions have names that start with double at signs @@ as a convention. To avoid confusion it is often recommended that you do not use names that start with @@.

Source: MSDN: Using Identifiers - Rules for Regular Identifiers.