This Oracle tutorial explains how to create a BEFORE UPDATE Trigger in Oracle with syntax and examples.
A BEFORE UPDATE Trigger skill that Oracle will fireplace this set off earlier than the UPDATE operation is executed.
The syntax to create a BEFORE UPDATE Trigger in Oracle/PLSQL is:
CREATE [ OR REPLACE ] TRIGGER trigger_name BEFORE UPDATE ON table_name [ FOR EACH ROW ] DECLARE -- variable declarations BEGIN -- trigger code EXCEPTION WHEN ... -- exception handling END;
Parameters or Arguments
OR REPLACE Optional. If specified, it approves you to re-create the trigger is it already exists so that you can trade the set off definition except issuing a DROP TRIGGER statement. trigger_name The identify of the trigger to create. BEFORE UPDATE It suggests that the trigger will fireplace before the UPDATE operation is executed. table_name The identify of the desk that the trigger is created on.
You can now not create a BEFORE trigger on a view. You can replace the :NEW values. You can no longer update the :OLD values.
See also how to create AFTER DELETE, AFTER INSERT, AFTER UPDATE, BEFORE DELETE, and BEFORE INSERT triggers. See also how to drop a trigger.
Let’s look at an example of how to create an BEFORE UPDATE set off the usage of the CREATE TRIGGER statement.
If you had a table created as follows:
CREATE TABLE orders ( order_id number(5), quantity number(4), cost_per_item number(6,2), total_cost number(8,2), updated_date date, updated_by varchar2(10) );
We ought to then use the CREATE TRIGGER announcement to create an BEFORE UPDATE trigger as follows:
TIP: When the usage of SQLPlus, you need to enter lower on a new line after the trigger. Otherwise, the script won’t execute.
CREATE OR REPLACE TRIGGER orders_before_update BEFORE UPDATE ON orders FOR EACH ROW DECLARE v_username varchar2(10); BEGIN -- Find username of person performing UPDATE on the table SELECT user INTO v_username FROM dual; -- Update updated_date field to current system date :new.updated_date := sysdate; -- Update updated_by field to the username of the person performing the UPDATE :new.updated_by := v_username; END; /