SAP HANA, as a cutting-edge in-memory database, supports advanced database programming features that help developers automate and streamline business processes. Among these features, triggers and events play a crucial role in enabling reactive programming within the database layer. This article explores what triggers and events are in SAP HANA, their use cases, and how to implement them effectively.
A trigger is a special kind of stored procedure that automatically executes (or “fires”) in response to specific changes to data in a table—such as INSERT, UPDATE, or DELETE operations. Triggers help enforce business rules, maintain audit trails, or replicate data without requiring application-level logic.
An event in SAP HANA is an operation or condition that can invoke certain actions like starting a procedure or triggering workflows. Events can be scheduled or fired based on specific database changes, enabling event-driven architectures within SAP HANA.
SAP HANA supports row-level triggers that execute once for each affected row. Triggers can be defined for the following events:
Here’s an example of creating an AFTER INSERT trigger that logs inserted records into an audit table:
CREATE TRIGGER trg_after_insert_sales
AFTER INSERT ON SALES_DATA
REFERENCING NEW ROW AS newRow
FOR EACH ROW
BEGIN
INSERT INTO SALES_AUDIT (SALE_ID, CUSTOMER_ID, AMOUNT, CHANGED_AT)
VALUES (:newRow.SALE_ID, :newRow.CUSTOMER_ID, :newRow.AMOUNT, CURRENT_TIMESTAMP);
END;
AFTER INSERT ON SALES_DATA: Trigger fires after a row is inserted into SALES_DATA.REFERENCING NEW ROW AS newRow: Accesses the inserted row.SALES_AUDIT capturing details of the change.Events in SAP HANA can be used to schedule or trigger execution of procedures or scripts. SAP HANA supports:
Example: Running a cleanup procedure every day at midnight.
CREATE EVENT cleanup_event
ON SCHEDULE
EVERY 1 DAY
STARTS CURRENT_DATE + 1
DO
CALL cleanup_old_records();
CREATE EVENT cleanup_event: Defines a new scheduled event.EVERY 1 DAY: Repeats daily.CALL cleanup_old_records(): Calls a stored procedure to perform cleanup.Triggers and events in SAP HANA provide powerful mechanisms for automating data-driven actions within the database. By carefully implementing these features, developers can ensure data integrity, automate workflows, and improve system responsiveness. Understanding when and how to use triggers and events is essential for building robust SAP HANA applications.