Oracle中Before和After触发器的例子

做一个表的insert的trigger，目的是只修改插入行的字段。

CREATE OR REPLACE TRIGGER TR_RME_SLOT
BEFORE INSERT ON RME_SLOT
FOR EACH ROW
BEGIN
IF (:NEW.POSITION >= 0 AND :NEW.POSITION <10) THEN
:NEW.SLOT_NAME := '0'||TO_CHAR(:NEW.POSITION);
ELSE
:NEW.SLOT_NAME := TO_CHAR(:NEW.POSITION);
END IF;
END;

在插入以前就需要修改插入行；在trigger实现中并不需要用到update语句

同时，如果要在trigger中实现对本表记录的修改，则需要这样写：

CREATE OR REPLACE TRIGGER TR_RME_SLOT
AFTER INSERT ON RME_SLOT
FOR EACH ROW
DECLARE
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
IF (:NEW.POSITION >= 0 AND :NEW.POSITION <10) THEN
UPDATE RME_SLOT SET SLOT_NAME = '0'||TO_CHAR(:NEW.POSITION) WHERE SLOT_ID=:NEW.SLOT_ID;
ELSE
UPDATE RME_SLOT SET SLOT_NAME = TO_CHAR(:NEW.POSITION) WHERE SLOT_ID=:NEW.SLOT_ID;
END IF;
COMMIT;
END;

注意多了一段DECLARE，同时在trigger结束时需要COMMIT

CREATE OR REPLACE TRIGGER tr_AfterUpdate
AFTER INSERT OR UPDATE
ON TEST_TRIGGER
FOR EACH ROW
DECLARE
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN

UPDATE TEST_TRIGGER
SET T_FACT = T_SALARY*(1-T_TAX)-T_EAT-T_HOUSE
WHERE T_NAME = :NEW.T_NAME;
COMMIT;

EXCEPTION
WHEN OTHERS THEN
-- Consider logging the error and then re-raise
RAISE;
END tr_testUpdate;