odbc_num_rows() will return the number of rows
in an ODBC result. This function will return -1 on error. For
INSERT, UPDATE and DELETE statements
odbc_num_rows() returns the number of rows
affected. For a SELECT clause this can be
the number of rows available.
Note: Using odbc_num_rows() to determine the
number of rows available after a SELECT will return -1 with many
drivers.