Identifiers have a maximum length of 128 bytes. They must be enclosed in double quotes, square brackets, or back quotes (`...`)
if any of the following conditions are true:
The identifier contains spaces.
The first character of the identifier is not an alphabetic character (as defined below).
The identifier is a reserved word.
The identifier contains characters other than alphabetic characters and digits.
Alphabetic characters includes the alphabet, the underscore character (_), at sign (@), number sign (#), and dollar sign ($). The database collation
sequence dictates which characters are considered alphabetic or digit characters.
The following characters are not permitted in identifiers:
Control characters (any character less than 0x20)
If the quoted_identifier database option is set to Off, double quotes are used to delimit SQL strings and cannot be used for
identifiers. However, you can use square brackets or back quotes to delimit identifiers, regardless of the setting of quoted_identifier.
The default setting for the quoted_identifier option is to Off for Open Client and jConnect connections; otherwise the default