[英]How to generate a range of dates in SQL Server
標題並不能完全反映我的意思,這可能是重復的。
這是一個很長的版本:給定客人的姓名,他們的注冊日期和他們的退房日期,如何為他們每天作為客人生成一行?
例:鮑勃簽入7/14,然后離開7/17。 我想要
('Bob', 7/14), ('Bob', 7/15), ('Bob', 7/16), ('Bob', 7/17)
作為我的結果。
謝謝!
我認為,為此特定目的,以下查詢與使用專用查找表一樣有效。
DECLARE @start DATE, @end DATE;
SELECT @start = '20110714', @end = '20110717';
;WITH n AS
(
SELECT TOP (DATEDIFF(DAY, @start, @end) + 1)
n = ROW_NUMBER() OVER (ORDER BY [object_id])
FROM sys.all_objects
)
SELECT 'Bob', DATEADD(DAY, n-1, @start)
FROM n;
結果:
Bob 2011-07-14
Bob 2011-07-15
Bob 2011-07-16
Bob 2011-07-17
大概您需要將此作為一個集合,而不是單個成員,因此這里是一種適應此技術的方法:
DECLARE @t TABLE
(
Member NVARCHAR(32),
RegistrationDate DATE,
CheckoutDate DATE
);
INSERT @t SELECT N'Bob', '20110714', '20110717'
UNION ALL SELECT N'Sam', '20110712', '20110715'
UNION ALL SELECT N'Jim', '20110716', '20110719';
;WITH [range](d,s) AS
(
SELECT DATEDIFF(DAY, MIN(RegistrationDate), MAX(CheckoutDate))+1,
MIN(RegistrationDate)
FROM @t -- WHERE ?
),
n(d) AS
(
SELECT DATEADD(DAY, n-1, (SELECT MIN(s) FROM [range]))
FROM (SELECT ROW_NUMBER() OVER (ORDER BY [object_id])
FROM sys.all_objects) AS s(n)
WHERE n <= (SELECT MAX(d) FROM [range])
)
SELECT t.Member, n.d
FROM n CROSS JOIN @t AS t
WHERE n.d BETWEEN t.RegistrationDate AND t.CheckoutDate;
----------^^^^^^^ not many cases where I'd advocate between!
結果:
Member d
-------- ----------
Bob 2011-07-14
Bob 2011-07-15
Bob 2011-07-16
Bob 2011-07-17
Sam 2011-07-12
Sam 2011-07-13
Sam 2011-07-14
Sam 2011-07-15
Jim 2011-07-16
Jim 2011-07-17
Jim 2011-07-18
Jim 2011-07-19
正如@Dems指出的那樣,這可以簡化為:
;WITH natural AS
(
SELECT ROW_NUMBER() OVER (ORDER BY [object_id]) - 1 AS val
FROM sys.all_objects
)
SELECT t.Member, d = DATEADD(DAY, natural.val, t.RegistrationDate)
FROM @t AS t INNER JOIN natural
ON natural.val <= DATEDIFF(DAY, t.RegistrationDate, t.CheckoutDate);
我通常在某些表上使用row_number()來達到目的。 所以:
select t.name, dateadd(d, seq.seqnum, t.start_date)
from t left outer join
(select row_number() over (order by (select NULL)) as seqnum
from t
) seq
on seqnum <= datediff(d, t.start_date, t.end_date)
seq的計算非常快,因為不需要計算或排序。 但是,您需要確保該表對於所有時間段都足夠大。
如果您有一個“ Tally”或“ Numbers”表,這樣的事情就變得很簡單。
SELECT Member, DatePresent = DATEADD(dd,t.N,RegistrationDate)
FROM @t
CROSS JOIN dbo.Tally t
WHERE t.N BETWEEN 0 AND DATEDIFF(dd,RegistrationDate,CheckoutDate)
;
以下是建立“ Tally”表的方法。
--===================================================================
-- Create a Tally table from 0 to 11000
--===================================================================
--===== Create and populate the Tally table on the fly.
SELECT TOP 11001
IDENTITY(INT,0,1) AS N
INTO dbo.Tally
FROM Master.sys.ALL_Columns ac1
CROSS JOIN Master.sys.ALL_Columns ac2
;
--===== Add a CLUSTERED Primary Key to maximize performance
ALTER TABLE dbo.Tally
ADD CONSTRAINT PK_Tally_N
PRIMARY KEY CLUSTERED (N) WITH FILLFACTOR = 100
;
--===== Allow the general public to use it
GRANT SELECT ON dbo.Tally TO PUBLIC
;
GO
有關SQL中的“ Tally”表及其如何用於替換While循環以及計數的遞歸CTE的“ Hidden RBAR”的更多信息,請參見以下文章。
這可能適用於:
with mycte as
(
select cast('2000-01-01' as datetime) DateValue, 'Bob' as Name
union all
select DateValue + 1 ,'Bob' as Name
from mycte
where DateValue + 1 < '2000-12-31'
)
select *
from mycte
OPTION (MAXRECURSION 0)
我將創建一個觸發器來創建額外的記錄,並在結帳時運行它。 另外,您可以每天做一次午夜工作(如果您需要數據庫中的最新信息)。
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