Every object in a database has a name. To work with an object, you must identify it by that name. In Transact-SQL, you use identifiers to specify the names of the objects you want to work with. Identifiers can have from 1 through 30 characters. The first character can be an alphabetic character (a-z or A-Z) or the symbols _ (underscore), @ (at sign), or # (pound sign). An identifier beginning with @ denotes a variable. An identifier beginning with # denotes a temporary object (table or procedure). After the first character, identifiers can include letters, digits, or the $, #, or _ symbols. For details about identifiers, see Identifiers in the Microsoft SQL Server Transact-SQL Reference.