插入或删除后的Oracle触发器

对不起我的英语

我有两张桌子：

Table1
id
table2_id
num
modification_date 

及

我想做一个触发器，在表1中插入或删除后更新表2.table1lastnum中的最后一个值num

我的触发器：

CREATE OR REPLACE TRIGGER TABLE1_NUM_TRG
  AFTER INSERT OR DELETE ON table1
  FOR EACH ROW
BEGIN
  IF INSERTING then

  UPDATE table2
  SET    table2num = :new.num
  WHERE  table2.id = :new.table2_id;

  ELSE

  UPDATE table2
  SET    table2num = (SELECT num FROM  (SELECT num FROM table1 WHERE table2_id = :old.table2_id ORDER BY modification_date DESC) WHERE ROWNUM <= 1)
  WHERE  table2.id = :old.table2_id;

  END IF;

END TABLE1_NUM_TRG; 

---

我做错了什么？

您遇到的是典型的变异表异常。在一行中，触发器Oracle不允许您对定义了触发器的表运行查询，因此导致此问题的是触发器的删除部分中的“针对表1选择”

有几种方法可以解决这个问题。在这种情况下，最好使用复合触发器，它看起来像：

CREATE OR REPLACE TRIGGER TABLE1_NUM_TRG
  FOR INSERT OR DELETE ON TABLE1
COMPOUND TRIGGER
  TYPE NUMBER_TABLE IS TABLE OF NUMBER;
  tblTABLE2_IDS  NUMBER_TABLE;

  BEFORE STATEMENT IS
  BEGIN
    tblTABLE2_IDS := NUMBER_TABLE();
  END BEFORE STATEMENT;

  AFTER EACH ROW IS
  BEGIN
    IF INSERTING THEN
      UPDATE TABLE2 t2
        SET    t2.TABLE2NUM = :new.NUM
        WHERE  t2.ID = :new.TABLE2_ID;
    ELSIF DELETING THEN
      tblTABLE2_IDS.EXTEND;
      tblTABLE2_IDS(tblTABLE2_IDS.LAST) := :new.TABLE2_ID;
    END IF;
  END AFTER EACH ROW;

  AFTER STATEMENT IS
  BEGIN
    IF tblTABLE2_IDS.COUNT > 0 THEN
      FOR i IN tblTABLE2_IDS.FIRST..tblTABLE2_IDS.LAST LOOP
        UPDATE TABLE2 t2
          SET t2.TABLE2NUM = (SELECT NUM
                                FROM (SELECT t1.NUM
                                        FROM TABLE1 t1
                                        WHERE t1.TABLE2_ID = tblTABLE2_IDS(i) 
                                        ORDER BY modification_date DESC)
                                WHERE ROWNUM = 1)
          WHERE t2.ID = tblTABLE2_IDS(i);
      END LOOP;
    END IF;
  END AFTER STATEMENT;
END TABLE1_NUM_TRG;

复合触发器允许处理语句前、行前、行后和语句后的每个计时点。请注意，定时点总是按照给定的顺序调用。当执行适当的SQL语句（即INSERT INTO TABLE1或DELETE FROM TABLE1）并触发此触发器时，要调用的第一个计时点将是BEFORE语句，BEFORE语句处理程序中的代码将分配一个PL/SQL表来保存一组数字。在这种情况下，PL/SQL表中存储的数字将是表1中的表2_ID值。例如，使用PL/SQL表而不是数组，因为表可以容纳不同数量的值，而如果使用数组，则必须事先知道需要存储多少个数字。我们无法预先知道有多少行会受到特定语句的影响，所以我们使用PL/SQL表

当到达AFTER EACH ROW计时点并且我们发现正在处理的语句是INSERT时，触发器将继续执行并对TABLE2执行必要的更新，因为这不会导致问题。但是，如果正在执行删除，则触发器会将TABLE1.TABLE2_ID保存到先前分配的PL/SQL表中。当最终到达AFTER语句计时点时，将遍历先前分配的PL/SQL表，并对找到的每个TABLE2\u ID执行适当的更新

---

.

您必须为delete定义一个before触发器。请尝试使用两个触发器

CREATE OR REPLACE TRIGGER INS_TABLE1_NUM_TRG
AFTER INSERT ON table1
FOR EACH ROW
 BEGIN
  UPDATE table2
  SET    table2num = :new.num
  WHERE  table2.id = :new.table2_id;
 END INS_TABLE1_NUM_TRG;


CREATE OR REPLACE TRIGGER DEL_TABLE1_NUM_TRG
BEFORE DELETE ON table1
FOR EACH ROW
 BEGIN
  UPDATE table2
  SET    table2num = (SELECT num FROM  
  (SELECT num FROM table1 WHERE   table2_id = :old.table2_id 
   ORDER BY modification_date DESC) 
   WHERE ROWNUM <= 1)
   WHERE  table2.id = :old.table2_id;
 END DEL_TABLE1_NUM_TRG;

---

@psaraj12答案是最好的IMHO，但在DELETE触发器中，我会使用：OLD符号，因为内部查询是不必要的，并且会显著降低触发器的速度：

... 
    BEFORE DELETE ON table1
    FOR EACH ROW
        UPDATE table2
        SET    table2num = :OLD.num
        WHERE  table2.id = :OLD.table2_id;
...

---

您试图在删除一行的表上运行SELECT语句。用谷歌搜索错误代码ORA-04091，您会得到很多答案。

CREATE OR REPLACE TRIGGER INS_TABLE1_NUM_TRG
AFTER INSERT ON table1
FOR EACH ROW
 BEGIN
  UPDATE table2
  SET    table2num = :new.num
  WHERE  table2.id = :new.table2_id;
 END INS_TABLE1_NUM_TRG;


CREATE OR REPLACE TRIGGER DEL_TABLE1_NUM_TRG
BEFORE DELETE ON table1
FOR EACH ROW
 BEGIN
  UPDATE table2
  SET    table2num = (SELECT num FROM  
  (SELECT num FROM table1 WHERE   table2_id = :old.table2_id 
   ORDER BY modification_date DESC) 
   WHERE ROWNUM <= 1)
   WHERE  table2.id = :old.table2_id;
 END DEL_TABLE1_NUM_TRG;

... 
    BEFORE DELETE ON table1
    FOR EACH ROW
        UPDATE table2
        SET    table2num = :OLD.num
        WHERE  table2.id = :OLD.table2_id;
...