><P
><B
>Note: </B
>      In most implementations of the <SPAN
CLASS="QUOTE"
>"not-a-number"</SPAN
> concept,
      <TT
CLASS="LITERAL"
>NaN</TT
> is not considered equal to any other numeric
      value (including <TT
CLASS="LITERAL"
>NaN</TT
>).  In order to allow
      <TT
CLASS="TYPE"
>numeric</TT
> 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="LITERA