使用 PL/SQL 块创建触发器时出错

Posted 2023-03-28

【中文标题】使用 PL/SQL 块创建触发器时出错

【英文标题】：Error while creating trigger using PL/SQL block

【发布时间】：2020-03-22 11:09:03

【问题描述】：

问题： fl_schedule(flno, 出发, dtime, 到达, atime, 价格)。

仅当航班号 CX7520 安排在周二、周五和周日时才允许插入或更新。

CREATE OR REPLACE TRIGGER flightsch_day
BEFORE INSERT OR UPDATE ON fl_schedule
FOR EACH ROW
WHEN (NEW.flno LIKE 'CX7520')
DECLARE 
    day NUMBER;
BEGIN
    day:=EXTRACT(weekday FROM :NEW.departs);
    IF day NOT IN(0,2,5) THEN  
        RAISE_APPLICATION_ERROR(-20000,'Flight number CX­7520 can be scheduled only on Tuesday, Friday and Sunday.');
    END IF;
END;
/

错误：

SQL> SHOW ERRORS;
Errors for TRIGGER FLIGHTSCH_DAY:

LINE/COL ERROR
-------- -----------------------------------------------------------------
4/10     PLS-00122: FROM as separator is allowed only with specific
         built-in functions

【参考方案1】：

为了能够在FOR EACH ROW 之后使用WHEN (NEW.flno = 'CX7520')，单个列flno 需要UPDATE OF flno

CREATE OR REPLACE TRIGGER flightsch_day
BEFORE INSERT OR UPDATE OF flno ON fl_schedule
FOR EACH ROW
WHEN (NEW.flno = 'CX7520')
DECLARE 
BEGIN
 IF TO_CHAR(:NEW.departs,'Dy','NLS_DATE_LANGUAGE=English') NOT IN ('Tue','Fri','Sun') THEN  
     RAISE_APPLICATION_ERROR(-20000,'Flight number CX­7520 can be scheduled only on Tuesday, Friday and Sunday.');
 END IF;
END;
/

或没有 WHEN.. 子句，将 :NEW.flno = 'CX7520' 转换为 IF 语句：

CREATE OR REPLACE TRIGGER flightsch_day
BEFORE INSERT OR UPDATE ON fl_schedule
FOR EACH ROW
DECLARE 
BEGIN
 IF NOT ( TO_CHAR(:NEW.departs,'Dy','NLS_DATE_LANGUAGE=English') IN ('Tue','Fri','Sun')
              AND :NEW.flno = 'CX7520' ) THEN  
    RAISE_APPLICATION_ERROR(-20000,'Flight number CX­7520 can be scheduled only on Tuesday, Friday and Sunday.');
 END IF;
END;
/

使用包含NLS_DATE_LANGUAGE 选项的日期缩写。 否则可能会遇到意外情况。 显示的错误源于在EXTRACT() 函数中使用weekday，其中day、month、year 允许用于日期类型变量，还允许使用hour、minute、second ..ETC。如果是日期时间类型变量，则允许，但

不允许

weekday