十字按日期

Question

連接SQL表我有如下表，表1

date   value 
------------------------- 
2015-01-01  0 
2015-01-02  0 
2015-01-03  0 
2015-01-04  0 

而且有一個表2

datestart  dateend   value 
------------------------------------- 
2015-01-02  2015-01-03  1 

我想獲得像以下

date   value 
------------------------- 
2015-01-01  0 
2015-01-02  1 
2015-01-03  1 
2015-01-04  0 

一個結果我試着用cross apply

select table1.date, temp.value 
from table1 
cross join 
(select table2.value from table2 where 
table2.startdate <= table1.date and table2.enddate > table1.date) as temp 

，但我最終

date   value 
------------------------- 
2015-01-02  1 
2015-01-03  1 

什麼是錯在我的代碼？

Answer 1

您可以使用左連接是這樣的：

select table1.date, coalesce(table2.value,0) Value 
from table1 
left join table2 
on table1.date between table2.startdate and table2.enddate 
order by 1 

雖然如果表2中有重疊的日期，它會變得雜亂。這可能不是你想要的，但如果你wa nted總結每個日期落入你會做這樣的事情的範圍內的所有值：

select table1.date, sum(coalesce(table2.value,0)) Value 
from table1 
left join table2 
on table1.date between table2.startdate and table2.enddate 
group by table1.date 

否則，你會得到你的輸出重複的日期。

Answer 2

你並不需要一個交叉連接，但左連接：

SELECT table1.date, table2.value 
FROM  table1 
LEFT JOIN table2 ON table1.date BETWEEN table2.startdate AND table2.enddate 

Answer 3

一個LEFT JOIN將在這裏做的：

SELECT table1.date, table2.value 
FROM table1 
LEFT JOIN 
table2 
ON table2.startdate <= table1.date 
AND table2.enddate > table1.date 

Answer 4

試試這個查詢。我已將列名稱日期更改爲mydate.I猜測date是一個關鍵字。

select t1.mydate, (case when t2.value is null then 0 else t2.value end) as value from table1 t1 left join table2 t2 
    on t1.mydate between t2.datestart and t2.dateend order by mydate; 

這裏是小提琴： http://sqlfiddle.com/#!9/85265/1