SQL Server：用日期填充表

Question

我正在使用 SQL Server。我有一个具有挑战性的问题（至少对我来说！）。

我有一张关于电视节目信息的表格；第一栏是节目的Title，第二栏是Genre，第三栏是Language，第四栏是节目的首播日期，格式为：2017-11-03。

我想做的是在从首映日期到未来 4 个月的日期范围内复制每一行。所以，如果当前行读取 2017-11-03，我想为这个范围内的每个日期复制这一行，然后为下一个电视节目（下一行）做同样的事情。

这可以在 SQL 中完成吗？

谢谢。

Answer 1

另一个选项是 CROSS APPLY 与 ad-hoc 计数表相结合

这将为源数据中的每条记录生成 4 个月的数据。

示例

Select A.*
      ,B.D
 From  YourTable A
 Cross Apply (
                Select Top (DateDiff(DAY,A.Premier,DateAdd(Month,4,A.Premier))+1) 
                       D=DateAdd(DAY,-1+Row_Number() Over (Order By (Select Null)),A.Premier) 
                 From  master..spt_values n1
              ) B

退货

-- 截断 ---

谷歌搜索...我爱露西于 1951 年 10 月 15 日首播应该先这样做。

Answer 2

您可以使用日历或日期表来处理这类事情。

内存中只有 152kb，您可以在一个表中包含 30 年的日期：

/* dates table */
declare @fromdate date = '20000101';
declare @years    int  = 30;
/* 30 years, 19 used data pages ~152kb in memory, ~264kb on disk */
;with n as (select n from (values(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) t(n))
select top (datediff(day, @fromdate,dateadd(year,@years,@fromdate)))
    [Date]=convert(date,dateadd(day,row_number() over(order by (select 1))-1,@fromdate))
into dbo.Dates
from n as deka cross join n as hecto cross join n as kilo
               cross join n as tenK cross join n as hundredK
order by [Date];
create unique clustered index ix_dbo_Dates_date
  on dbo.Dates([Date]);

无需执行创建表的实际步骤，您可以在 common table expression 中使用类似的方法，只需这样做：

declare @fromdate date = '20170101';
declare @years    int  = 4;
;with n as (select n from (values(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) t(n))
, dates as (
  select top (datediff(day, @fromdate,dateadd(year,@years,@fromdate)))
      [Date]=convert(date,dateadd(day,row_number() over(order by (select 1))-1,@fromdate))
  from n as deka cross join n as hecto cross join n as kilo
                cross join n as tenK cross join n as hundredK
   order by [Date]
)

---

像这样使用：

select d.date, t.*
from dates d
  inner join tv_shows t
    on d.date >= t.premiere_date
   and d.date <= dateadd(month,4,t.premiere_date)

rextester 演示：http://rextester.com/XSRG45354

返回：

+------------+-------+---------+----------+---------------+
|    date    | title |  genre  | language | premiere_date |
+------------+-------+---------+----------+---------------+
| 2017-11-03 | one   | example | english  | 2017-11-03    |
| 2017-11-04 | one   | example | english  | 2017-11-03    |
| 2017-11-05 | one   | example | english  | 2017-11-03    |
| 2017-11-06 | one   | example | english  | 2017-11-03    |
....                
| 2018-02-28 | one   | example | english  | 2017-11-03    |
| 2018-03-01 | one   | example | english  | 2017-11-03    |
| 2018-03-02 | one   | example | english  | 2017-11-03    |
| 2018-03-03 | one   | example | english  | 2017-11-03    |
+------------+---------------+---------+----------+---------------+

数字和日历表参考：

• Generate a set or sequence without loops - 2 - Aaron Bertrand
• The "Numbers" or "Tally" Table: What it is and how it replaces a loop - Jeff Moden
• Creating a Date Table/Dimension in sql Server 2008 - David Stein
• Calendar Tables - Why You Need One - David Stein
• Creating a date dimension or calendar table in sql Server - Aaron Bertrand

Answer 3

最简单的方法是使用数字表。这是构建足够大的一种方法：

with n as (
      select 0 as n union all
      select n.n from n where n.n < 50
     )
select tv.*, dateadd(week, n.n, tv.premierdate) as showdate
from tvshows tv join
     n
     on dateadd(week, n.n, tv.premierdate) <= dateadd(month, 4, tv.premierdate);