Naming Conventions in SQL Server

Restrict the remaining characters in your identifiers to alphabetic characters (A–Z, a–z, and Unicode Standard 3.2 letters), numeric digits (0–9), and the underscore character (_). The dollar sign ($) character, while allowed, is not advisable.

• SQL Server variable names that start with the at sign (@),
• temporary tables and procedures that start with the number sign (#)
• global temporary tables and procedures that begin with the double number sign (##).
• Many built-in T-SQL functions and system variables have names that begin with a double at sign (@@),such as @@ERROR and @@IDENTITY.