<TT
CLASS="LITERAL"
>NaN</TT
>, meaning
     <SPAN
CLASS="QUOTE"
>"not-a-number"</SPAN
>.  Any operation on <TT
CLASS="LITERAL"
>NaN</TT
>
     yields another <TT
CLASS="LITERAL"
>NaN</TT
>.  When writing this value
     as a constant in an SQL command, you must put quotes around it,
     for example <TT
CLASS="LITERAL"
>UPDATE table SET x = 'NaN'</TT
>.  On input,
     the string <TT
CLASS="LITERAL"
>NaN</TT
> is recognized in a case-insensitive manner.
    </P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
