Desktop Survival Guide
by Graham Williams
The Believe Num Rows option is an oddity required for some ODBC drivers and appears to be associated with the pre-fetch behaviour of these drivers. The default is to activate the check box (i.e., Believe Num Rows is True). However, if you find that you are not retrieveing all rows from the source table, the the ODBC driver may be using a pre-fetch mechanism that does not ``correctly'' report the number of rows (it is probably only reporting the number of rows limited to the size of the pre-fetch). In these cases deactivate the Believe Num Rows check box. See Section 30.8 for more details. Another solution is to either disable the pre-fetch option of the driver, or to increase its count. For example, in connecting through the Netezza ODBC driver the configuration window is available, where you can change the default Prefetch Count value.