如何使用Oracle触发器（和域表）代替检查约束来强制执行列范围

Question

此触发器（Oracle 12c）旨在停止插入和更新表（MainTable aka Room）中的行，其中列（价格）大于一个变量。变量的值取决于另一列（类型）。有三种类型（S，D，K），'类型'的最大允许价格分别为100,150和200。该触发器通过引用具有两列和三行的域表（DomainTable又名RoomType），如下[roomTypeCode（S，D，K），maxPrice（100,150,200）]并确保：

.. .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）;

这是我的尝试不起作用。

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; 

我的错误信息：

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. 

感谢您的帮助！

Answer 1

当您创建触发器时，您会看到类似'编译时出现警告'或'错误：检查编译器日志'的消息。此时，您可以执行show errors以查看编译失败的原因，或查看SQL Developer的编译器日志窗口。

当您插入或更新the invalid trigger is automatically recompiled，但由于它仍然无效，您会收到ORA-04098错误。你仍然可以看到什么是错的通过查询user_errors观点：

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

与您的代码中给出了三个错误;只显示每个的第一行：

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: 

正如大卫·费伯在评论中指出，第一个错误是因为你在你的声明部分的select语句;也许在这一点上审查the structure of a subprogram将是有用的。

第二个错误是因为您的IF没有THEN关键字，第三个错误是因为您没有END IF。只是清理你必须正确地申报和填充的变量是什么，你会得到这样的：

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; 

你并不真正需要三个变量，虽然，你可以查询你感兴趣的房型：

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; 

我也采取了\n出来的，不管用什么插件可能把那两个文字字符，而不是换行的错误消息。

您可能还想考虑捕获no_data_found并引发您自己的例外情况，因为这会表明新房型不存在，因此无论如何都无效。