Question

我有一张下表table1

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

并有一个table2

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

我想得到如下结果

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

我尝试使用交叉申请

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

但我最终还是

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

我的代码有什么问题？

Answer 1

您不需要交叉加入，但需要左连接：

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

Answer 2

LEFT JOIN将在此处执行：

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

Answer 3

您可以像这样使用左连接：

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

如果你在表2中有重叠的日期，它会变得混乱。这可能不是你想要的，但是如果你想要将每个日期所属的范围的所有值相加，你会做这样的事情：

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

否则您将在输出中获得重复日期。

Answer 4

尝试此查询。我已将列名日期更改为mydate。我猜日期是关键字。

  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;

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

按日期交叉连接sql表

4 个答案: