简单的oracle触发器

Question

简单的一个.我有点像PLSql的新手,oracle的错误信息永远不会太有帮助.

我想做一个简单的触发器来更新具有当前日期的列,即表的"修改日期"列.虽然得到一个奇怪的错误.

这个想法很简单

create table test1 (tcol varchar2(255), tcol2 varchar2(255))

CREATE OR REPLACE TRIGGER testTRG
AFTER INSERT OR UPDATE ON test1
FOR EACH ROW
BEGIN 
     update test1
     set tcol2 =  to_char(sysdate)
     where tcol = :OLD.tcol;
END;

insert into test1 (tcol) values ('test1');

这会弹出错误:

ORA-04091: table RAIDBIDAT_OWN.TEST1 is mutating, trigger/function may not see it
ORA-06512: at "RAIDBIDAT_OWN.TESTTRG", line 2
ORA-04088: error during execution of trigger 'RAIDBIDAT_OWN.TESTTRG'

有人可以快速解决这个问题吗？

干杯,

F.

Answer 1

你的情况:

SQL> create table test1 (tcol varchar2(255), tcol2 varchar2(255))
  2  /

Table created.

SQL> CREATE OR REPLACE TRIGGER testTRG
  2  AFTER INSERT OR UPDATE ON test1
  3  FOR EACH ROW
  4  BEGIN
  5       -- Your original trigger
  6       update test1
  7       set tcol2 =  to_char(sysdate)
  8       where tcol = :OLD.tcol;
  9  END;
 10  /

Trigger created.

SQL> insert into test1 (tcol) values ('test1');
insert into test1 (tcol) values ('test1')
            *
ERROR at line 1:
ORA-04091: table [schema].TEST1 is mutating, trigger/function may not see it
ORA-06512: at "[schema].TESTTRG", line 3
ORA-04088: error during execution of trigger '[schema].TESTTRG'

托尼的建议几乎是正确的,但不幸的是它没有编译:

SQL> CREATE OR REPLACE TRIGGER testTRG
  2  AFTER INSERT OR UPDATE ON test1
  3  FOR EACH ROW
  4  BEGIN
  5       -- Tony's suggestion
  6       :new.tcol2 :=  sysdate;
  7  END;
  8  /
CREATE OR REPLACE TRIGGER testTRG
                          *
ERROR at line 1:
ORA-04084: cannot change NEW values for this trigger type

因为您只能在每行前触发器中更改新值:

SQL> create or replace trigger testtrg
  2    before insert or update on test1
  3    for each row
  4  begin
  5    :new.tcol2 := sysdate;
  6  end;
  7  /

Trigger created.

SQL> insert into test1 (tcol) values ('test1');

1 row created.

SQL> select * from test1
  2  /

TCOL
------------------------------------------------------------------------------------------
TCOL2
------------------------------------------------------------------------------------------
test1
13-09-2010 12:37:24


1 row selected.

问候,Rob.