Trigger Example

We illustrate Oracle's syntax for creating a trigger through an example based on the following two tables:

CREATE TABLE T4 (a INTEGER, b CHAR(10));

CREATE TABLE T5 (c CHAR(10), d INTEGER);

We create a trigger that may insert a tuple into T5 when a tuple is inserted into T4. Specifically, the trigger checks whether the new tuple has a first component 10 or less, and if so inserts the reverse tuple into T5:

CREATE TRIGGER trig1
    AFTER INSERT ON T4
    REFERENCING NEW AS newRow
    FOR EACH ROW
    WHEN (newRow.a <= 10)
    BEGIN
        INSERT INTO T5 VALUES(:newRow.b, :newRow.a);
    END trig1;
.
run;

Notice that we end the CREATE TRIGGER statement with a dot and run, as for all PL/SQL statements in general. Running the CREATE TRIGGER statement only creates the trigger; it does not execute the trigger. Only a triggering event, such as an insertion into T4 in this example, causes the trigger to execute.