A  string  operator  concatenates,   compares   character-string
  expressions,  or  tests string inclusion in another string.  The
  result is either a string or a Boolean value.

  String Operators:

    operator | example |    result
    --------------------------------------------
       +       A +  B   String that is the concatenation of strings

       <>      A <> B   TRUE if strings A and B have unequal ASCII
                        values

       <       A <  B   TRUE if the ASCII value of string A is less
                        than that of string B

       <=      A <= B   TRUE if the ASCII value of string A is less
                        than or equal to that of string B

       >       A >  B   TRUE if the ASCII value of string A is greater
                        than that of string B

       >=      A >= B   TRUE if the ASCII value of string A is greater
                        than or equal to that of string B

       IN      A IN B   TRUE if the string A is contained in string B
                        (This is identical to INDEX(B,A) <> 0)

       NOT IN  A NOT IN B
                        TRUE if the string A is not contained in string B
                        (This is identical to INDEX(B,A) = 0)