Identifiers

Identifiers are used to name user- (and some system-) defined SQL language objects including databases, tables, domains, columns, column aliases, stored procedures, and user-defined functions. An identifier is formed as a combination of letters, digits, underscore character ('_' ) and dollar sign ($) beginning with a letter or underscore. All identifiers in SQL are case-insensitive. Thus, CUSTOMER, Customer, and customer all refer to the same item. Reserved words cannot be used as identifiers.

identifier:
               {letter | '_'}[letter | digit | '_' | '$']...