多个表的数据库约束

Question

说我有以下表格：

CREATE TABLE [Weeks] 
(
    [Id] INT NOT NULL IDENTITY,
    CONSTRAINT [PK_Weeks] PRIMARY KEY ([Id])
);

CREATE TABLE [Days] 
(
    [Id] INT NOT NULL IDENTITY,
    [WeekId] INT NULL,

    CONSTRAINT [PK_Days] PRIMARY KEY ([Id]),
    CONSTRAINT [FK_Days_Weeks_WeekId] 
        FOREIGN KEY ([WeekId]) REFERENCES [Weeks] ([Id])
);

CREATE TABLE [ReplacedDayInWeek] 
(
    [Id] INT NOT NULL IDENTITY,
    [WeekId] INT NOT NULL,
    [DayId] INT NOT NULL,
    [ReplacedDayId] INT NOT NULL,

    CONSTRAINT [PK_ReplacedDayInWeek] PRIMARY KEY ([Id]),
    CONSTRAINT [FK_ReplacedDayInWeek_Days_DayId] 
        FOREIGN KEY ([DayId]) REFERENCES [Days] ([Id]),
    CONSTRAINT [FK_ReplacedDayInWeek_Weeks_WeekId] 
        FOREIGN KEY ([WeekId]) REFERENCES [Weeks] ([Id]),
    CONSTRAINT [FK_ReplacedDayInWeek_Weeks_ReplacedWeekId] 
        FOREIGN KEY ([ReplacedWeekId]) REFERENCES [Weeks] ([Id])
);

表ReplacedDayInWeek包含特定周的一天，由另一天替换。

我如何创建一个SQL约束（或者可能是另一个基于SQL的解决方案），以确保我只能使用与DayInWeek同一周的DayId将行插入WeekId？

我正在寻找对源数据库进行最少量更改的解决方案。我更喜欢在存储过程之上更改一个表或表。

Answer 1

这种数据结构对我来说毫无意义。您有两个表中的天和周之间的映射。

你应该只将一周存储在一个表中，然后在另一个表中查找。

也就是说，您可以使用两个表之间的日/周额外约束来执行您想要的操作：

CREATE TABLE [Days] 
(
    [Id] INT NOT NULL IDENTITY,
    [WeekId] INT NULL,

    CONSTRAINT [PK_Days] PRIMARY KEY ([Id]),
    CONSTRAINT [FK_Days_Weeks_WeekId] 
        FOREIGN KEY ([WeekId]) REFERENCES [Weeks] ([Id]),
    CONSTRAINT UNQ_Days_WeekId_Id UNIQUE (WeekId, Id)
);

CREATE TABLE [DaysInWeek] 
(
    [Id] INT NOT NULL IDENTITY,
    [WeekId] INT NOT NULL,
    [DayId] INT NOT NULL,

    CONSTRAINT [PK_DaysInWeek] PRIMARY KEY([Id]),
    CONSTRAINT [FK_DaysInWeek_Days_WeekId_DayId] 
        FOREIGN KEY (WeekId, DayId) REFERENCES Days(WeekId, Id),
    CONSTRAINT [FK_DaysInWeek_Weeks_WeekId] 
        FOREIGN KEY ([WeekId]) REFERENCES [Weeks] ([Id])
);