变异表错误只是一种痛苦。你要做的是相当棘手的。这里有一种方法：
将列添加到 teams 参加人数。
维护此列 insert / update ，和 delete 触发器打开 participateteams .
编写一个用户定义的函数来获取给定团队的计数。
添加 check 约束 participateteams 使用用户定义的函数。

逻辑上正确的触发条件是：-

CREATE OR REPLACE TRIGGER TRIG_CHK
AFTER INSERT OR UPDATE OF teamPlace ON participateteams
FOR EACH ROW
DECLARE
participants NUMBER;
BEGIN
 select count(*) into participants from participateteams where :New.eventName = 
 participateteams.eventName;
    if(:NEW.teamplace>participants) then
        RAISE_APPLICATION_ERROR(-20250,'O lugar da equipa é inválido');
    end if;
End;    
update participateteams set teamPlace = 2 where eventName = 'B';

但是，当它在尝试更新表participateteams时出现变异表错误时，为了解决这个棘手的问题，我所做的是：-
步骤1：声明包头中所需的表列

CREATE OR REPLACE PACKAGE PKG_TEAMS AS
v_eventName participateteams.eventName%type;
v_teamPlace participateteams.teamPlace%type;
end;

步骤2：初始化行级触发器中的变量

CREATE OR REPLACE TRIGGER TRG_row
AFTER INSERT OR UPDATE OF teamPlace
ON participateteams
FOR EACH ROW
BEGIN
PKG_TEAMS.v_eventName := :NEW.eventName;
PKG_TEAMS.v_teamPlace := :NEW.teamPlace;
END;

步骤3：现在，使用全局初始化变量，而不是使用：新的伪列

CREATE OR REPLACE TRIGGER TRG_stmt
AFTER INSERT OR UPDATE OF teamPlace ON participateteams
DECLARE 
v_participants NUMBER;
BEGIN
SELECT COUNT(*) INTO v_participants FROM participateteams
WHERE eventName = PKG_TEAMS.v_eventName;
 if(PKG_TEAMS.v_teamPlace>v_participants) then
            RAISE_APPLICATION_ERROR(-20250,'CANNOT UPDATE,AGAINST RULES');
        end if;
End;