我试图添加一个 检查约束 ，但到目前为止，我只是失败了。解决这个问题的方法是什么：

讯息1046，第15级，州1，第6行

在这种情况下，不允许子查询。仅允许标量表达式。

这是代码：

ALTER TABLE dbo.PropertySeasonDiscount ADD CONSTRAINT
[CC_PropertySeasonDiscount_MadeFrom_MadeTo]
CHECK (
    (SELECT COUNT(PropertySeasonDiscountId) FROM dbo.PropertySeasonDiscounts apsdeb 
        WHERE 
            (apsdeb.PropertySeasonId = PropertySeasonId) AND
            (
                (apsdeb.ValidForReservationsMadeTo >= ValidForReservationsMadeFrom AND ValidForReservationsMadeFrom >= apsdeb.ValidForReservationsMadeFrom) OR
                (apsdeb.ValidForReservationsMadeFrom <= ValidForReservationsMadeTo AND ValidForReservationsMadeTo <= apsdeb.ValidForReservationsMadeTo)
            )
    ) = 0
);