Trigger if updating then

25-Mar-2020 17:29

If no WHEN clause is supplied, the SQL statements are executed every time the trigger fires.

The BEFORE or AFTER keyword determines when the trigger actions will be executed relative to the insertion, modification or removal of the associated row.

CREATE OR REPLACE TRIGGER emp Before Update BEFORE UPDATE OF location ON emp REFERENCING OLD AS o NEW AS n FOR EACH ROW WHEN (n.salary IS NULL OR n.salary = o.salary) SET n.salary = DECFLOAT(o.salary) / CASE o.location WHEN 'Boston' THEN 1.2 UPDATE emp SET location = 'Boston' WHERE name = 'Jason'; UPDATE emp SET location = 'Toronto' WHERE name = 'Jill'; UPDATE emp SET location = 'New York', salary = 63000 WHERE name = 'John'; SELECT * FROM emp ORDER BY name; NAME RANK LOCATION SALARY ---------- ----------- ---------- ----------- Jack Now, the only problem the above approach has is that our logic is spread across multiple objects.

Every time we re-evaluate the living costs in different cities we need to remember to update both triggers. Certainly what we could do in this case is to store the modifiers in a table and perhaps use a function to encapsulate much of the logic, but then, this is a simple example.

Returns a Boolean value that indicates whether an INSERT or UPDATE attempt was made on a specified column of a table or view.

UPDATE() is used anywhere inside the body of a Transact-SQL INSERT or UPDATE trigger to test whether the trigger should execute certain actions.

CREATE or REPLACE TRIGGER emp_after_update AFTER UPDATE OF empid ON emp FOR EACH ROW DECLARE BEGIN update emp_backup set empid = :new.empid where empid = :old.empid; DBMS_OUTPUT.

trigger if updating then-56

At this time SQLite supports only FOR EACH ROW triggers, not FOR EACH STATEMENT triggers.Hence explicitly specifying FOR EACH ROW is optional.FOR EACH ROW implies that the SQL statements specified in the trigger may be executed (depending on the WHEN clause) for each database row being inserted, updated or deleted by the statement causing the trigger to fire.Both the WHEN clause and the trigger actions may access elements of the row being inserted, deleted or updated using references of the form "NEW.column-name" and "OLD.column-name", where column-name is the name of a column from the table that the trigger is associated with.OLD and NEW references may only be used in triggers on events for which they are relevant, as follows: If a WHEN clause is supplied, the SQL statements specified are only executed if the WHEN clause is true.

At this time SQLite supports only FOR EACH ROW triggers, not FOR EACH STATEMENT triggers.Hence explicitly specifying FOR EACH ROW is optional.FOR EACH ROW implies that the SQL statements specified in the trigger may be executed (depending on the WHEN clause) for each database row being inserted, updated or deleted by the statement causing the trigger to fire.Both the WHEN clause and the trigger actions may access elements of the row being inserted, deleted or updated using references of the form "NEW.column-name" and "OLD.column-name", where column-name is the name of a column from the table that the trigger is associated with.OLD and NEW references may only be used in triggers on events for which they are relevant, as follows: If a WHEN clause is supplied, the SQL statements specified are only executed if the WHEN clause is true.A database trigger is a stored procedure that automatically executes whenever an event occurs. Oracle initiates an ‘AFTER INSERT’ trigger after an insert event has been occurred and an ‘AFTER UPDATE’ trigger after an update event has been occurred.