很多与时间有关的查询都要求标识重叠的时期，下面的示例中，出于统计账单或其他目的，Sessions表跟踪应用程序的用户会话。会话表示接入到互联网的链接，例如一些互联网的供应商按照链接时间收费。该表包含主键（keycol），应用程序名称（app），用户名（usr），开始时间（starttime），结束时间（endtime）
创建表：
USE [tempdb]
GO
/****** Object: Table [dbo].[Sessions] Script Date: 08/12/2011 10:56:52 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[Sessions]
(
[keycol] [int] IDENTITY(1, 1)
NOT NULL ,
[app] [varchar](10) NOT NULL ,
[usr] [varchar](10) NOT NULL ,
[starttime] [datetime] NOT NULL ,
[endtime] [datetime] NOT NULL ,
PRIMARY KEY CLUSTERED ( [keycol] ASC )
WITH ( PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON,
ALLOW_PAGE_LOCKS = ON ) ON [PRIMARY] ,
CONSTRAINT [IX_Sessions] UNIQUE NONCLUSTERED
( [app] ASC, [usr] ASC, [starttime] ASC, [endtime] ASC, [keycol] ASC )
WITH ( PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON,
ALLOW_PAGE_LOCKS = ON ) ON [PRIMARY]
)
ON [PRIMARY]
GO
SET ANSI_PADDING OFF
GO
ALTER TABLE [dbo].[Sessions] WITH CHECK ADD CHECK (([endtime]>[starttime]))
GO
插入数据：
SET IDENTITY_INSERT [Sessions] ON
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 2 ,
'app1' ,
'user1' ,
'2006/6/12 8:30:00' ,
'2006/6/12 10:30:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 4 ,
'app1' ,
'user1' ,
'2006/6/12 9:00:00' ,
'2006/6/12 9:30:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 6 ,
'app1' ,
'user1' ,
'2006/6/12 9:15:00' ,
'2006/6/12 9:30:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 8 ,
'app1' ,
'user1' ,
'2006/6/12 10:45:00' ,
'2006/6/12 11:30:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 3 ,
'app1' ,
'user2' ,
'2006/6/12 8:30:00' ,
'2006/6/12 8:45:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 5 ,
'app1' ,
'user2' ,
'2006/6/12 9:15:00' ,
'2006/6/12 10:30:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 7 ,
'app1' ,
'user2' ,
'2006/6/12 10:30:00' ,
'2006/6/12 14:30:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 9 ,
'app1' ,
'user2' ,
'2006/6/12 11:00:00' ,
'2006/6/12 11:30:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 10 ,
'app2' ,
'user1' ,
'2006/6/12 8:30:00' ,
'2006/6/12 8:45:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 12 ,
'app2' ,
'user1' ,
'2006/6/12 11:45:00' ,
'2006/6/12 12:00:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 14 ,
'app2' ,
'user1' ,
'2006/6/12 12:45:00' ,
'2006/6/12 13:30:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 16 ,
'app2' ,
'user1' ,
'2006/6/12 14:00:00' ,
'2006/6/12 16:30:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 11 ,
'app2' ,
'user2' ,
'2006/6/12 9:00:00' ,
'2006/6/12 9:30:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 13 ,
'app2' ,
'user2' ,
'2006/6/12 12:30:00' ,
'2006/6/12 14:00:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 15 ,
'app2' ,
'user2' ,
'2006/6/12 13:00:00' ,
'2006/6/12 14:00:00'
)
INSERT [Sessions]
( [keycol] ,
[app] ,
[usr] ,
[starttime] ,
[endtime]
)
VALUES ( 17 ,
'app2' ,
'user2' ,
'2006/6/12 15:30:00' ,
'2006/6/12 17:00:00'
)
SET IDENTITY_INSERT [Sessions] OFF
下面将会讨论三个涉及重叠的技术：标识重叠，分组重叠和最大重叠