一、触发器引起ORA-04091
原因:在行级触发器中,不能查询自身表
场景重现:通过触发器实现test_count表中统计test表中行数
--创建子表
create table TEST
(id NUMBER, name varchar2(100), primary key (id));
--创建统计表
create table test_count (test_count int);
--创建触发器
CREATE OR REPLACE TRIGGER T_TEST
AFTER INSERT OR DELETE ON TEST
FOR EACH ROW
DECLARE
A NUMBER;
BEGIN
SELECT COUNT(*) INTO A FROM TEST;
UPDATE TEST_COUNT SET TEST_COUNT = A;
END T_TEST;
模拟错误:
INSERT INTO TEST (ID,NAME)VALUES(2,'abc');
ORA-04091: table CHF.TEST is mutating, trigger/function may not see it
ORA-06512: at "CHF.T_TEST", line 2
ORA-04088: error during execution of trigger 'CHF.T_TEST'
处理方法:
通过自治事务实现(修改触发器)
CREATE OR REPLACE TRIGGER T_TEST
AFTER INSERT OR DELETE ON TEST
FOR EACH ROW
DECLARE
A NUMBER;
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
SELECT COUNT(*) INTO A FROM TEST;
UPDATE TEST_COUNT SET TEST_COUNT = A;
COMMIT;
END T_TEST;
PRAGMA AUTONOMOUS_TRANSACTION
当前的触发器作为已有事务的子事务运行,子事务自治管理,子事务的commit、rollback操作不影响父事务的状态
二、oracle触发器中增删改查本表
(1)只有before insert触发器中才可以查询或更新本表
create or replace trigger tri_test_ins
before insert
on test
for each row
declare
v_cnt integer;
begin
select count(*) into v_cnt from test;
dbms_output.put_line('test count:'||to_char(v_cnt));
update test set a9='99';
end;
执行insert后,只有当前插入的记录值不是99,其它的记录都被更新成了99。
(2)before/after update、before/after delete、after insert5种情况都不可以查询或更新本表。
(3)使用自治事务可以实现任意触发器查本表。但不能实现在自治事务中更新本表。
查询本表的情况是最常见的。
create or replace trigger tri_test_ins
after update
on test
for each row
declare
v_cnt integer;
PRAGMA AUTONOMOUS_TRANSACTION;
begin
begin
select count(*) into v_cnt from test;
dbms_output.put_line('test count:'||to_char(v_cnt));
end;
end;
(4)使用自治事务可以实现新增或删除本表的记录。这种情况一般不会用到。
三、自治事务查本表使用:new错误
create or replace
trigger tr_mtn_basic_data_change
after insert
on mtn_basic_data_change
for each row
declare
vc_change_operator varchar2(10);
PRAGMA AUTONOMOUS_TRANSACTION;
begin
select change_operator into vc_change_operator from mtn_basic_data_change where scn=:new.scn;
update mtn_basic_data_change_log set change_operator=vc_change_operator;
commit;
end;
由于insert mtn_basic_data_change还没有提交,select change_operator into vc_change_operator from mtn_basic_data_change where scn=:new.scn语句报1403错。
解决方法:修改触发器如下:
create or replace
trigger tr_mtn_basic_data_change
after insert
on mtn_basic_data_change
for each row
declare
vc_change_operator varchar2(10);
begin
vc_change_operator:=:new.change_operator;
update mtn_basic_data_change_log set change_operator=vc_change_operator;
end;
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