>May I know what is the different on execution between using WHERE and HAVING clause?

On VFP you can use HAVING without GROUP BY clause.
HAVING
- is not optimizable;
- is not called in query analyse phase;
- is called only one time for any record put into result cursor.

This is very usefull like last filter condition into a complex query.

In your problem, i think you move the record pointer in origin table, and vfp copy a empty record.

Fabio