Simple identifier. The first character in a simple identifier must not be a digit or underscore.
<simple_identifier> ::= <first_character>[<identifier_tail_character>...]
first_character, identifier_tail_character
Simple identifiers are always converted into uppercase characters in the database. For this reason, simple identifiers are not case sensitive.
Reserved keywords must not be used in simple identifiers.
If the name of a database object is to contain lowercase letters, special characters, reserved keywords, or blanks, the identifier must be specified as a special identifier (enclosed in double quotation marks).