Single-table queries are updatable provided that

There are no JOINs, UNIONs, INTERSECTs, or MINUS operations.

There is no DISTINCT key word in the SELECT. (This restriction may be relaxed if all the fields of a unique index are projected.)

Everything in the SELECT clause is a simple column reference or a calculated field; no aggregation is allowed.

The table referenced in the FROM clause is either an updatable base table or an updatable view.

There is no GROUP BY or HAVING clause.

There are no subqueries that reference the table in the FROM clause and no correlated subqueries.

Any ORDER BY clause can be satisfied with an index (a simple single-field index for DBF tables).