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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 definitions, read-only. 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. |
