Check 约束可以与另一个表相关吗? [英] Can a Check constraint relate to another table?

问题描述

假设我有一个名为 ProjectTimeSpan 的表(我没有，只是作为示例！)包含 StartDate 和 EndDate 列>.

Let's say I have one table called ProjectTimeSpan (which I haven't, just as an example!) containing the columns StartDate and EndDate.

而且我有另一个名为 SubProjectTimeSpan 的表，其中还包含名为 StartDate 和 EndDate 的列，我想在其中设置一个 检查约束，这使得无法将 StartDate 和 EndDate 设置为 ProjectTimeSpan.StartDate 到 ProjectTimeSpan.EndDate

And that I have another table called SubProjectTimeSpan, also containing columns called StartDate and EndDate, where I would like to set a Check constraint that makes it impossible to set StartDate and EndDate to values "outside" the ProjectTimeSpan.StartDate to ProjectTimeSpan.EndDate

一种知道另一个表值的检查约束......

Kind of a Check constraint that knows about another tables values...

这可能吗?

推荐答案

为了回应您对 GSerg 的回答的评论，这里有一个使用函数的检查约束示例:

In response to your comment on GSerg's answer, here's an example check constraint using a function:

alter table YourTable
add constraint chk_CheckFunction
check (dbo.CheckFunction() = 1)

您可以在哪里定义函数，例如:

Where you can define the function like:

create function dbo.CheckFunction()
returns int
as begin
    return (select 1)
end

该函数允许引用其他表.

The function is allowed to reference other tables.

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