如何在 oracle PL/SQL 中设置列​​删除触发器？

Question

我尝试过这样做：

CREATE OR REPLACE TRIGGER DLL_No_Column_Del
BEFORE DROP ON SCHEMA
BEGIN
 IF ORA_DICT_OBJ_TYPE = 'COLUMN'
 THEN
    INSERT INTO column_del_attempt VALUES
    (
        user,
        SYSDATE,
        ora_dict_obj_name
    );
    RAISE_APPLICATION_ERROR(-20100, 'No column deletion allowed on table ' || ORA_DICT_OBJ_NAME);
 END IF;
END;

然后像这样删除列：

ALTER TABLE emp_copy
DROP COLUMN employee_id;

但它不起作用

Answer 1

创建一个自治程序来记录事件：

CREATE PROCEDURE log_system_event(
  p_user_name   IN COLUMN_DEL_ATTEMPT.USER_NAME%TYPE,
  p_object_name IN COLUMN_DEL_ATTEMPT.OBJECT_NAME%TYPE,
  p_object_type IN COLUMN_DEL_ATTEMPT.OBJECT_TYPE%TYPE
)
AS
  PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
  INSERT INTO column_del_attempt (
    user_name,
    datetime,
    object_name,
    object_type
  ) VALUES (
    p_user_name,
    SYSDATE,
    p_object_name,
    p_object_type
  );
  COMMIT;
END log_system_event;
/

然后您可以从触发器中调用它（在 ALTER 事件上，而不是在 DROP 事件上）：

CREATE TRIGGER DLL_No_Column_Del
BEFORE ALTER ON SCHEMA
BEGIN
  IF ora_dict_obj_name = 'EMP_COPY' AND ORA_DICT_OBJ_TYPE = 'TABLE' THEN
    log_system_event( login_user, ora_dict_obj_name, ORA_DICT_OBJ_TYPE );
    
    RAISE_APPLICATION_ERROR(-20100, 'No column deletion allowed on table ' || ORA_DICT_OBJ_NAME);
  END IF;
END;
/

那么，如果你这样做：

ALTER TABLE emp_copy DROP COLUMN employee_id;

它会引发异常：

ORA-04088: error during execution of trigger 'FIDDLE_SPRKWOBAQONFKBBYMKLX.DLL_NO_COLUMN_DEL'
ORA-00604: error occurred at recursive SQL level 1
ORA-20100: No column deletion allowed on table EMP_COPY
ORA-06512: at line 5

然后：

SELECT * FROM column_del_attempt;

输出：

用户名 |日期时间 |对象名 | OBJECT_TYPE :---------------------------- | :-------- | :------------ | :---------- FIDDLE_SPRKWOBAQONFKBBYMKLX | 20 年 12 月 18 日 | EMP_COPY |桌子

db小提琴here

---

更新

要获取ALTER DDL 语句的文本according to AskTom，您可以使用V$OPEN_CURSOR 动态性能视图来获取DDL 语句的文本，然后您可以对其进行过滤：

CREATE PROCEDURE log_system_event(
  p_user_name   IN COLUMN_DEL_ATTEMPT.USER_NAME%TYPE,
  p_object_name IN COLUMN_DEL_ATTEMPT.OBJECT_NAME%TYPE,
  p_object_type IN COLUMN_DEL_ATTEMPT.OBJECT_TYPE%TYPE,
  p_text        IN COLUMN_DEL_ATTEMPT.TEXT%TYPE
)
AS
  PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
  INSERT INTO column_del_attempt (
    user_name,
    datetime,
    object_name,
    object_type,
    text
  ) VALUES (
    p_user_name,
    SYSDATE,
    p_object_name,
    p_object_type,
    p_text
  );
  COMMIT;
END log_system_event;
/

然后：

CREATE TRIGGER DLL_No_Column_Del
BEFORE ALTER ON SCHEMA
DECLARE
  v_text VARCHAR2(4000);
BEGIN
  SELECT SQL_TEXT
  INTO   v_text
  FROM   V$OPEN_CURSOR;
  
  IF REGEXP_LIKE( v_text, '^ALTER\s+TABLE\s+("?)EMP_COPY\1\s+DROP\s+', 'i') THEN
    log_system_event( login_user, ora_dict_obj_name, ORA_DICT_OBJ_TYPE, v_text );
    
    RAISE_APPLICATION_ERROR(-20100, 'No column deletion allowed on table ' || ORA_DICT_OBJ_NAME);
  END IF;
END;
/

（但是，db<>fiddle、SQLFiddle 和 Oracle 的 LiveSQL 都没有授予使用 V$OPEN_CURSOR dynamic performance view 的权限，所以我无法对此进行测试。）

Answer 2

最终解决方案：

CREATE TABLE column_del_attempt (
  user_name   VARCHAR2(30),
  datetime    DATE,
  object_name VARCHAR2(30),
  object_type VARCHAR2(30)
)
/
CREATE OR REPLACE PROCEDURE log_system_event(
  p_user_name   IN COLUMN_DEL_ATTEMPT.USER_NAME%TYPE,
  p_object_name IN COLUMN_DEL_ATTEMPT.OBJECT_NAME%TYPE,
  p_object_type IN COLUMN_DEL_ATTEMPT.OBJECT_TYPE%TYPE
)
AS
  PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
  INSERT INTO column_del_attempt (
    user_name,
    datetime,
    object_name,
    object_type
  ) VALUES (
    p_user_name,
    SYSDATE,
    p_object_name,
    p_object_type
  );
  COMMIT;
END log_system_event;
/

CREATE OR REPLACE TRIGGER DLL_No_Column_Del
BEFORE ALTER ON SCHEMA
DECLARE
    n NUMBER;
    sql_text_list ora_name_list_t;
    drop_exist BOOLEAN := FALSE;
BEGIN
n := ora_sql_txt(sql_text_list);
FOR i in 1..n LOOP
    IF sql_text_list(i) LIKE '%DROP%' THEN 
        drop_exist := TRUE;
    END IF;
END LOOP;
  IF drop_exist THEN
    log_system_event( login_user, ora_dict_obj_name, ORA_DICT_OBJ_TYPE );
    RAISE_APPLICATION_ERROR(-20100, 'No column deletion allowed on table ' || ORA_DICT_OBJ_NAME);
  END IF;
END;
/
-- for tests:
/*
ALTER TABLE emp_copy ADD birth_date DATE NOT NULL;
ALTER TABLE emp_copy DROP COLUMN birth_date;

SELECT * FROM column_del_attempt;
*/