btrott mentioned that RaiseError is the recommended way to
check for errors but that you could alternatively check the
error return value for each DBI method call. Here's subtle
case where not using RaiseError can bite you:
while ($sth->fetch) {
print join("\t", $id, $name, $phone), "\n";
}
On the face of it, this will repeatedly call fetch until
there is nothing more to fetch. In fact, fetch will return
undef either when all rows have been fetched
or when there was an error. Here's a couple of
cases where fetch might successfully return a number of
rows then return undef for an error:
- you selected a calculated value (eg: total/count) which
caused a divide by zero error
- one of your columns is a long text field that exceeds
the default buffer size (LongReadLen) and because you left
the LongTruncOK option at default, it throws an error
In each case, you might see some output and mistakenly
believe you'd seen all matching rows. The moral - always
set RaiseError and wrap DBI calls using eval
