请解释:
<代码>:新和:old instart Code.
<代码>:新和:old为便于查阅特定栏目中新的和旧数值的假记录。 如果我有一张桌子的话,我会有一个桌子。
CREATE TABLE foo (
foo_id NUMBER PRIMARY KEY,
bar VARCHAR2(10),
baz VARCHAR2(10)
);
页: 1
INSERT INTO foo( foo_id, bar, baz )
VALUES( 1, Bar 1 , Baz 1 );
之后再加插触发器
:new.foo_id will be 1
:new.bar will be Bar 1
:new.baz will be Baz 1
......
:old.foo_id will be NULL
:old.bar will be NULL
:old.baz will be NULL
如果是的话,你会更新这一行文。
UPDATE foo
SET baz = Baz 2
WHERE foo_id = 1
然后在之前更新浏览级触发器
:new.foo_id will be 1
:new.bar will be Bar 1
:new.baz will be Baz 2
......
:old.foo_id will be 1
:old.bar will be Bar 1
:old.baz will be Baz 1
如果我删除行文
DELETE FROM foo
WHERE foo_id = 1
之后删除“增长触发器”,
:new.foo_id will be NULL
:new.bar will be NULL
:new.baz will be NULL
......
:old.foo_id will be 1
:old.bar will be Bar 1
:old.baz will be Baz 2
In Plain English:
它们是使你能够从一栏(旧)和一栏(新)如何取用。
旧的和新的数值在贝都因和AFTER增长触发器中都有。 新的一栏值可分配到底盘旋器中,但不能在固定电离层触发器中(因为触发信号在发射气流触发器之前生效)。 如果主角电流引发新哥伦的改变,那么同一声明发射的AFTER输电触发器就看到了BeitFORE输电机的改变。
也可在WHEN条款的“Bolean”表述中使用校正名称。 殖民地必须先于旧的和新的限定性,然后才能在触发体内使用,但在使用WHEN条款或REFERENCING方案中的限定词时,不得允许殖民地。
<代码>:old记录载有触发说明执行前的数值,:new记录载有执行后的价值。
update set col1=<10/code>, 10为new。 该栏的现值和现值为旧数。
插入一个字面,有固定的旧价值,只有新值,删除的是新价值,只有旧价值。
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