Identifiers are names of objects in the database, such as user IDs, tables, and columns. Identifiers have a maximum length of 128 bytes.
You must enclose identifiers in double quotes if any of the following conditions are true:
The identifier contains spaces.
The first character of the identifier is not an alphabetic character. The database collation sequence dictates which characters are considered alphabetic or digit characters.
The identifier contains a reserved word. See Reserved words.
The identifier contains characters other than alphabetic characters and digits.
You can only use a single backslash in an identifier if it is used as an escape character.