如何使用Oracle觸發器（和域表）代替檢查約束來強制執行列範圍

Question

此觸發器（Oracle 12c）旨在停止插入和更新表（MainTable aka Room）中的行，其中列（價格）大於一個變量。變量的值取決於另一列（類型）。有三種類型（S，D，K），'類型'的最大允許價格分別爲100,150和200。該觸發器通過引用具有兩列和三行的域表（DomainTable又名RoomType），如下[roomTypeCode（S，D，K），maxPrice（100,150,200）]並確保：

.. .IF new MainTable.type ='S'，THEN new MainTable.price < DomainTable.maxPrice（S）;

... IF new MainTable.type ='D'，THEN new MainTable.price < DomainTable.maxPrice（D）;

... IF new MainTable.type ='K'，THEN new MainTable.price < DomainTable.maxPrice（K）;

這是我的嘗試不起作用。

CREATE TRIGGER Room_Type_Price_Range 
    BEFORE INSERT OR UPDATE ON room 
    REFERENCING NEW AS newRec 
    FOR EACH ROW 
    DECLARE 
    SELECT maxPrice INTO singleRmMax FROM RoomType WHERE RoomTypeCode = 'S'; 
    SELECT maxPrice INTO doubleRmMax FROM RoomType WHERE RoomTypeCode = 'D'; 
    SELECT maxPrice INTO kingRmMax FROM RoomType WHERE RoomTypeCode = 'K'; 
    BEGIN 
    IF ( (:newRec.type = 'S' AND :newRec.price > singleRmMax) 
     OR (:newRec.type = 'D' AND :newRec.price > doubleRmMax) 
     OR (:newRec.type = 'K' AND :newRec.price > kingRmMax) 
     ) 
     RAISE_APPLICATION_ERROR(-20001, 'Price constraint violated. 
      \nCannot Insert/Update in this table.'); 
    END; 

我的錯誤信息：

04098. 00000 - "trigger '%s.%s' is invalid and failed re-validation" 
*Cause: A trigger was attempted to be retrieved for execution and was 
      found to be invalid. This also means that compilation/authorization 
      failed for the trigger. 
*Action: Options are to resolve the compilation/authorization errors, 
      disable the trigger, or drop the trigger. 

感謝您的幫助！

Answer 1

當您創建觸發器時，您會看到類似'編譯時出現警告'或'錯誤：檢查編譯器日誌'的消息。此時，您可以執行show errors以查看編譯失敗的原因，或查看SQL Developer的編譯器日誌窗口。

當您插入或更新the invalid trigger is automatically recompiled，但由於它仍然無效，您會收到ORA-04098錯誤。你仍然可以看到什麼是錯的通過查詢user_errors觀點：

select line, position, text 
from user_errors 
where type = 'TRIGGER' 
and name = 'ROOM_TYPE_PRICE_RANGE' 
order by sequence; 

與您的代碼中給出了三個錯誤;只顯示每個的第一行：

LINE POSITION TEXT 
---- -------- ------------------------------------------------------------------------------------------------- 
    2  5 PLS-00103: Encountered the symbol "SELECT" when expecting one of the following: 
    10  9 PLS-00103: Encountered the symbol "RAISE_APPLICATION_ERROR" when expecting one of the following: 
    11  50 PLS-00103: Encountered the symbol ";" when expecting one of the following: 

正如大衛·費伯在評論中指出，第一個錯誤是因爲你在你的聲明部分的select語句;也許在這一點上審查the structure of a subprogram將是有用的。

第二個錯誤是因爲您的IF沒有THEN關鍵字，第三個錯誤是因爲您沒有END IF。只是清理你必須正確地申報和填充的變量是什麼，你會得到這樣的：

DECLARE 
    singleRmMax RoomType.MaxPrice%TYPE; 
    doubleRmMax RoomType.MaxPrice%TYPE; 
    kingRmMax RoomType.MaxPrice%TYPE; 
BEGIN 
    SELECT maxPrice INTO singleRmMax FROM RoomType WHERE RoomTypeCode = 'S'; 
    SELECT maxPrice INTO doubleRmMax FROM RoomType WHERE RoomTypeCode = 'D'; 
    SELECT maxPrice INTO kingRmMax FROM RoomType WHERE RoomTypeCode = 'K'; 

    IF ( (:newRec.type = 'S' AND :newRec.price > singleRmMax) 
    OR (:newRec.type = 'D' AND :newRec.price > doubleRmMax) 
    OR (:newRec.type = 'K' AND :newRec.price > kingRmMax) 
    ) THEN 
    RAISE_APPLICATION_ERROR(-20001, 'Price constraint violated. 
     \nCannot Insert/Update in this table.'); 
    END IF; 
END; 

你並不真正需要三個變量，雖然，你可以查詢你感興趣的房型：

DECLARE 
    roomTypeMax RoomType.MaxPrice%TYPE; 
BEGIN 
    SELECT maxPrice INTO roomTypeMax 
    FROM RoomType 
    WHERE RoomTypeCode = :newRec.type; 

    IF :newRec.price > roomTypeMax THEN 
    RAISE_APPLICATION_ERROR(-20001, 
     'Price constraint violated. Cannot Insert/Update in this table.'); 
    END IF; 
END; 

我也採取了\n出來的，不管用什麼插件可能把那兩個文字字符，而不是換行的錯誤消息。

您可能還想考慮捕獲no_data_found並引發您自己的例外情況，因爲這會表明新房型不存在，因此無論如何都無效。