Using DBD::Oracle, I consistently get $sth->rows returning 0 even when there's data for it. The reason that is, consulting the documentation, is that rows reliably returns the number of rows affected by a statement that *modifies* data, not on SELECT ones:

For `SELECT' statements, it is generally not possible
to know how many rows will be returned except by
fetching them all.  Some drivers will return the
number of rows the application has fetched so far, but
others may return -1 until all rows have been fetched.
So use of the `rows' method or `$DBI::rows' with
`SELECT' statements is not recommended.

You'll just have to count 'em manually, looks like.

HTH

Philosophy can be made out of anything. Or less -- Jerry A. Fodor