A quoted character string literal is a string of printable
    characters enclosed in single quotation marks. The maximum length
    of a character string is 1,024 octets. An unqualified character
    string must contain characters only from the literal character
    set of that session.

    The printable ASCII characters consist of:

    o  Uppercase alphabetic characters:

       A-Z

    o  Lowercase alphabetic characters:

       a-z

    o  Numerals:

       0-9

    o  Special characters:

       ! @ # $ % ^ & * ( ) - _ = + ` ~

       [ ] { } ; : " \ | / ? > < . ,

    For a list of the printable characters for DEC_MCS, see the
    OpenVMS documentation for users; for a list of printable
    characters for the other supported character sets, see the
    standard for that character set.

    Use a pair of single quotation marks to enclose a character
    string literal. If you use double quotation marks, an
    informational message is displayed, indicating that double
    quotation marks are nonstandard. Double quotation marks are
    passed as delimited identifiers if the quoting rules are set
    to ANSI/ISO SQL.