SQL 服务器唯一键约束 Date/Time 跨度

Question

如何为以下 table 设置唯一键约束以确保 Date/BeginTime 和 Date/EndTime 之间的 date/time 跨度不与其他记录重叠？如果我需要添加一个计算列，什么数据类型和计算？

Column Name   Data Type
Date          date
BeginTime     time(7)
EndTime       time(7)

谢谢。

Answer 1

我认为您无法在 SQL 服务器中使用 UNIQUE 约束来做到这一点。 Postgres 具有此功能，但要在 SQL 服务器中实现它，您必须使用触发器。由于您的问题是 "how can I do this using a unique key constraint"，因此正确答案是 "you can't"。如果你问过 "how can I enforce this non-overlapping constraint"，这里有答案。

Answer 2

-- this is a unique key that allows for null in EndTime field
--  This Unique Index could be clusteres optionally instead of the traditional primary key being clustered 
CREATE UNIQUE NONCLUSTERED INDEX  
[UNQ_IDX_Date_BeginTm_EndTm_UniqueIndex_With_Null_EndTime] ON [MyTableName]
(
    [Date] ASC,
    [BeginTime] ASC,
    [EndTime] ASC
) 

GO


-- this is a traditional PK Constraint that is clustered but EndTime is
--- Not Null
-- it is possible that this table would not have a traditional Primary Key
ALTER TABLE dbo.MyTable ADD CONSTRAINT
    PK_Date_BeginTm_EndTm_EndTimeIsNotNull PRIMARY KEY CLUSTERED 
    (
    Date,
    BeginTime,
    EndTime
    ) 

GO

-- HINT - Control your BeginTime and EndTime secconds and milliseconds at 
-- all insert and read points 
-- you want 13:01:42.000  and 13:01:42.333  to evaluate and compare the
-- exact way you expect from a KEY perspective

Answer 3

Alexander Kuznetsov 展示了一种可能的方法。 Storing intervals of time with no overlaps.

另请参阅 Joe Celko 的文章：Contiguous Time Periods

这里是table和第一个区间：

CREATE TABLE dbo.IntegerSettings(SettingID INT NOT NULL,
  IntValue INT NOT NULL,
  StartedAt DATETIME NOT NULL,
  FinishedAt DATETIME NOT NULL,
  PreviousFinishedAt DATETIME NULL,

  CONSTRAINT PK_IntegerSettings_SettingID_FinishedAt 
      PRIMARY KEY(SettingID, FinishedAt),

  CONSTRAINT UNQ_IntegerSettings_SettingID_PreviousFinishedAt
      UNIQUE(SettingID, PreviousFinishedAt),

  CONSTRAINT FK_IntegerSettings_SettingID_PreviousFinishedAt
    FOREIGN KEY(SettingID, PreviousFinishedAt)
    REFERENCES dbo.IntegerSettings(SettingID, FinishedAt),

  CONSTRAINT CHK_IntegerSettings_PreviousFinishedAt_NotAfter_StartedAt
      CHECK(PreviousFinishedAt <= StartedAt),

  CONSTRAINT CHK_IntegerSettings_StartedAt_Before_FinishedAt 
      CHECK(StartedAt < FinishedAt)
);

INSERT INTO dbo.IntegerSettings
    (SettingID, IntValue, StartedAt, FinishedAt, PreviousFinishedAt)
VALUES(1, 1, '20070101', '20070103', NULL);

约束强制执行这些规则：

一个设置只能有一个第一个间隔
下一个window必须在上一个结束后开始
两个不同的 windows 不能引用一个和前一个 window 相同的

SQL 服务器唯一键约束 Date/Time 跨度

SQL Server Unique Key Constraint Date/Time Span

sql-server

sql-server-2014