TPSQLUpdateSQL applies data updates on behalf of queries or stored procedures that can't
post updates directly.
Use a TPSQLUpdateSQL object to provide SQL statements used to update read-only datasets
represented by TPSQLQuery component. A dataset is read-only
either by design or circumstance. If a dataset is read-only by design, the application itself does not
provide a user interface for updating data, but may institute a programmatic scheme behind the scenes.
If a dataset is read-only by circumstance, it indicates that the PostgreSQL returned a read-only result
set. This usually happens for queries made against multiple tables. Such queries are, by SQL-92
TPSQLUpdateSQL provides a mechanism for circumventing what some developers consider an
SQL-92 limitation. It enables a developer to provide INSERT, UPDATE, and DELETE statements for
performing separate update queries on otherwise read-only result sets in such a manner that the
separate update queries are transparent to the end user.
In practical application, a TPSQLUpdateSQL object is placed on a data module or form, and
linked to a TPSQLQuery component through that component's UpdateObject property. If the
UpdateObject property points to a valid TPSQLUpdateSQL object, the SQL statements
belonging to the update object are automatically applied.