<TT
CLASS="LITERAL"
>NaN</TT
>).
      In order to allow floating-point values to be sorted and used
      in tree-based indexes, <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> treats
      <TT
CLASS="LITERAL"
>NaN</TT
> values as equal, and greater than all
      non-<TT
CLASS="LITERAL"
>NaN</TT
> values.
     </P
></BLOCKQUOTE
></DIV
><P
>     <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> also supports the SQL-standard
     notations <TT
CLASS="TYPE"
>float</TT
> and
     <TT
CLASS="TYPE"
>float(<TT
CLASS=