OLD Context Variables
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Indicates a current column value in an
DELETE operation. Available in triggers only.
Name of a column in the affected row
Description: Triggers support two context variables:
OLD context variable refers to the current or previous value of a column in an
Context variables are often used to compare the values of a column before and after it is modified. Context variables can be used anywhere a regular variable can be used.
Example: The following script is a trigger that fires after the
EMPLOYEE table is updated, and compares an employee’s old and new salary. If there is a change in salary, the trigger inserts an entry in the
CREATE TRIGGER SAVE_SALARY_CHANGE FOR EMPLOYEE AFTER UPDATE AS BEGIN IF (OLD.SALARY <> NEW.SALARY) THEN INSERT INTO SALARY_HISTORY (EMP_NO, CHANGE_DATE, UPDATER_ID, OLD_SALARY, PERCENT_CHANGE) VALUES (OLD.EMP_NO, ‘NOW’, USER, OLD.SALARY, (NEW.SALARY - OLD.SALARY) * 100 / OLD.SALARY); END ;
For more information about creating triggers, see CREATE TRIGGER.