Question

如果您有两张桌子，那就让我们说Doors and House。

桌子通过外键（门到门）连接。限制是一个房子有2到10个门。

在数据级别强制执行此操作的最佳方法是什么？

Answer 1

create table houses (id int primary key)
create table doors (
    id int primary key,
    house_id int references houses(id)
    )

create trigger doorsCondition on doors 
instead of insert
AS
    declare @max int, @min int
    select @max = max(i), @min = min(i) from (
        select count(1) i from (
            select house_id from doors where house_id = ANY (select house_id from inserted)
            union all
            select house_id from inserted) subquery
        group by house_id) subQuery2


    if (@max <= 10 and @min >= 2)
        insert into doors select * from inserted
    else
        print 'The insert violates business constraint'

和相应的删除触发器。您可以将它们合并为一个，但在这个简单的场景中，我不确定它是否值得考虑所有事情。

将行数限制在一个范围内

1 个答案: