问题描述
如果我有这样的表结构:
If I have a table structure like this:
ProductCode Date
Foo 4/1/2012
Foo 4/2/2012
Foo 4/3/2012
Foo 4/6/2012
Foo 4/7/2012
Foo 4/8/2012
Foo 4/9/2012
Foo 4/10/2012
Foo 4/15/2012
Foo 4/16/2012
Foo 4/17/2012
有没有办法查询给定 ProductCode
和 Date
的日期范围(假设范围必须是连续的)?换句话说,对于这个表,Foo 存在于 3 个日期范围内:4/1-4/3
;4/6-4/10
;和 4/15-4/17
,我正在寻找给定日期的日期范围.
Is there a way to query for the date range for a given ProductCode
and Date
(assuming that ranges MUST be sequential)? In other words, for this table, Foo exists on 3 date ranges: 4/1-4/3
; 4/6-4/10
; and 4/15-4/17
and I'm looking for the date range given a date.
请注意 Foo
没有日期的 4/4
、4/5
、4/11
>、4/12
、4/13
和 4/14
.
Please note that Foo
doesn't have date's 4/4
, 4/5
, 4/11
, 4/12
, 4/13
and 4/14
.
示例:ProductCode=Foo, Date=4/2
将返回 4/1-4/3
因为条目是连续的.ProductCode=Foo, Date=4/4
不会返回任何内容ProductCode=Foo, Date=4/7
将返回 4/6-4/10
因为条目是连续的.ProductCode=Foo, Date=4/12
不会返回任何内容
等
Examples:
ProductCode=Foo, Date=4/2
would return 4/1-4/3
because the entries are sequential.
ProductCode=Foo, Date=4/4
would return nothing
ProductCode=Foo, Date=4/7
would return 4/6-4/10
because the entries are sequential.
ProductCode=Foo, Date=4/12
would return nothing
etc.
推荐答案
本来可以使用 LAG,如果 SQL Server 2005 支持它.不幸的是,LAG 窗口函数仅适用于 SQL Server 2012,并且 PostgreSQL 8.4 及更高版本 ;-)
Could have used LAG, if SQL Server 2005 supported it. Unfortunately LAG window function works on SQL Server 2012 only, and PostgreSQL 8.4 and above ;-)
我认为可以在 SQL Server 2005 上运行,SQLFiddle 不支持 SQL 2005,只尝试了 SQLFiddle 的 SQL Server 2008,而不是 2012:
Works on SQL Server 2005 I supposed, SQLFiddle has no SQL 2005 support, tried SQLFiddle's SQL Server 2008 only, not 2012:
with DetectLeaders as
(
select cr.ProductCode, CurRowDate = cr.Date, PrevRowDate = pr.Date
from tbl cr
left join tbl pr
on pr.ProductCode = cr.ProductCode AND cr.Date = DATEADD(DAY,1,pr.Date)
),
MembersLeaders as
(
select *,
MemberLeader =
(select top 1 CurRowDate
from DetectLeaders nearest
where nearest.PrevRowDate is null
and nearest.ProductCode = DetectLeaders.ProductCode
and DetectLeaders.CurRowDate >= nearest.CurRowDate
order by nearest.CurRowDate desc)
from DetectLeaders
)
select BeginDate = MIN(CurRowDate), EndDate = MAX(CurRowDate)
from MembersLeaders
where MemberLeader =
(select MemberLeader
from MembersLeaders
where ProductCode = 'Foo' and CurRowDate = '4/7/2012')
现场测试:http://sqlfiddle.com/#!3/3fd1f/1一个>
基本上它是这样工作的:
Basically this is how it works:
PRODUCTCODE CURROWDATE PREVROWDATE MEMBERLEADER
Foo 2012-04-01 2012-04-01
Foo 2012-04-02 2012-04-01 2012-04-01
Foo 2012-04-03 2012-04-02 2012-04-01
Foo 2012-04-06 2012-04-06
Foo 2012-04-07 2012-04-06 2012-04-06
Foo 2012-04-08 2012-04-07 2012-04-06
Foo 2012-04-09 2012-04-08 2012-04-06
Foo 2012-04-10 2012-04-09 2012-04-06
Foo 2012-04-15 2012-04-15
Foo 2012-04-16 2012-04-15 2012-04-15
Foo 2012-04-17 2012-04-16 2012-04-15
Bar 2012-05-01 2012-05-01
Bar 2012-05-02 2012-05-01 2012-05-01
Bar 2012-05-03 2012-05-02 2012-05-01
Bar 2012-05-06 2012-05-06
Bar 2012-05-07 2012-05-06 2012-05-06
Bar 2012-05-08 2012-05-07 2012-05-06
Bar 2012-05-09 2012-05-08 2012-05-06
Bar 2012-05-10 2012-05-09 2012-05-06
Bar 2012-05-15 2012-05-15
Bar 2012-05-16 2012-05-15 2012-05-15
Bar 2012-05-17 2012-05-16 2012-05-15
http://sqlfiddle.com/#!3/35818/11
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