# SQL.
create table pqr
(
  x  numeric(9,0)  not null
, y  unsigned int  not null
)
insert into pqr values( 0 , 0 )


# Perl
$n = 1;
#  Works.
$dbh->do( q/UPDATE pqr SET x = ?/ , undef , $n );

$n = 2;
#  Fails;
$dbh->do( q/UPDATE pqr SET y = ?/ , undef , $n );

$n = 3;
#  works (same as %s, this is all string in the end).
$dbh->do( sprintf q/UPDATE pqr SET y = %d/ , $n );