   expr IN (value,...)
Returns 1 if expr is any of the values in the IN list,
else returns 0.  If all values are constants, they are
evaluated according to the type of expr and sorted. The search for the
item then is done using a binary search. This means IN is very quick
if the IN value list consists entirely of constants.  If expr
is a case-sensitive string expression, the string comparison is performed in
case-sensitive fashion.
