編譯觸發時表達式是錯誤類型的錯誤消息

Question

我收到以下錯誤。不知道爲什麼會出現這個錯誤。請建議：

SQL> CREATE OR REPLACE TRIGGER test_trigger 
    2 
    3 BEFORE INSERT OR UPDATE OF DRIVER_NUM 
    4 
    5 ON test_driver FOR EACH ROW 
    7 DECLARE 
    8 
    9 Invalid_Number EXCEPTION; 
10 
11 PRAGMA EXCEPTION_INIT(Invalid_Number , -01722); 
12 
13  BEGIN 
14 
15  IF TO_NUMBER(:NEW.DRIVER_NUM) THEN 
16 
17   :NEW.DRIVER_NUM := TO_NUMBER(:NEW.DRIVER_NUM) ; 
18 
19  END IF; 
20 
21  EXCEPTION 
22 
23   WHEN Invalid_Number THEN 
24 
25    :NEW.DRIVER_NUM := NULL; 
26 
27  END; 
/
28 
Warning: Trigger created with compilation errors. 
SQL> show errors 
Errors for TRIGGER TEST_TRIGGER: 
LINE/COL ERROR 
-------- ----------------------------------------------------------------- 
9/2  PL/SQL: Statement ignored 
9/5  PLS-00382: expression is of wrong type 

Answer 1

IF TO_NUMBER(:NEW.DRIVER_NUM) THEN不是一個有效的表達式。

我猜你想要的東西，如：

IF TO_NUMBER(:NEW.DRIVER_NUM) > 0 THEN

但更重要的是，你的代碼沒有任何意義可言。我不明白爲什麼你分配一個列的內容相同的列本身：

:NEW.DRIVER_NUM := TO_NUMBER(:NEW.DRIVER_NUM); 

如果DRIVER_NUM已經是一個數字列，這並不在所有的意義（數字轉換成數？）。

如果DRIVER_NUM是例如一個VARCHAR這會是個偶數讀少

Answer 2

嘗試取消「DRIVER_NUM的」，用這樣的：

/* Formatted on 1/06/2011 9:10:59 (QP5 v5.114.809.3010) */ 
CREATE OR REPLACE TRIGGER test_trigger 
    BEFORE INSERT OR UPDATE ON test_driver 
    FOR EACH ROW 
DECLARE 
    INVALID_NUMBER EXCEPTION; 
    PRAGMA EXCEPTION_INIT (INVALID_NUMBER, -01722); 
BEGIN 
    IF TO_NUMBER (:NEW.DRIVER_NUM) 
    THEN 
     :NEW.DRIVER_NUM := TO_NUMBER (:NEW.DRIVER_NUM); 
    END IF; 
EXCEPTION 
    WHEN INVALID_NUMBER 
    THEN 
     :NEW.DRIVER_NUM := NULL; 
END; 

如果我明白你正在嘗試做的，你想創建一個觸發器只有某些領域？這不是必要的，或者甚至對於這個問題來說都是可能的。

Answer 3

我的猜測是你試圖確保VARCHAR2列DRIVER_NUM只包含有效數字 - 如果沒有，將其設置爲空。如果這是你想要的東西，試試這個：

CREATE OR REPLACE TRIGGER test_trigger 
BEFORE INSERT OR UPDATE OF DRIVER_NUM 
ON test_driver 
FOR EACH ROW 
DECLARE 
    Dummy NUMBER; 
    Invalid_Number EXCEPTION; 
    PRAGMA EXCEPTION_INIT(Invalid_Number , -01722); 
BEGIN 
    Dummy := TO_NUMBER(:NEW.DRIVER_NUM) ; 
EXCEPTION 
    WHEN Invalid_Number THEN 
     :NEW.DRIVER_NUM := NULL; 
END;