如何计算天数？

Question

使用SQL Server 2005

表1

ID FromDate ToDate 

001 23-02-2009 25-02-2009 
001 27-02-2009 29-02-2009 
002 12-02-2009, 25-03-2009 

...，

表2

ID Name Total 

001 Raja 30 
002 Ravi 22 

我想一日总量为PERSONID

尝试查询，

SELECT 
    table2.Id, table2.name, table2.total, 
    datediff(day, table1.fromdate, table2.todate) 
FROM table1 
LEFT OUTER JOIN table2 ON table1.personid = table2.personid 

获取输出

ID Name Total Days 

001 Raja 30 3 
001 Raja 30 3 
..., 

应该总天数和它应该在一行内显示，

注：假如我选择特定时期日期意味着它应该显示，只有天

例如

其中26-02-2009之间日期03-03-2009，它应该显示

ID Name Total Days 

001 Raja 30 3 
..., 

由于正在采取日期25-02-2009后，

Expected Output 

ID Name Total Days 

001 Raja 30 6 
002 Ravi 22 16 

如何修改我的查询？

Answer 1

DATEDIFF给出了天差的两个日期之间的数，所以在相同的方式1和3之间的不同是2（3 - 1 = 2），DATEDIFF（d）实际上是D2-D1。因此，为了补偿要算上额外的一天，你需要DATEADD一天或者（TODATE或FROM日期），以抵消你日期：

SELECT table2.id, table2.Name, table2.Total, SUM(DATEDIFF(d, DATEADD(d, -1, table1.FromDate), table1.ToDate)) 
    FROM table1 
     INNER JOIN table2 ON table1.id = table2.id 
    GROUP BY table2.id, table2.Name, table2.Total 

Answer 2

SELECT table2.Id, table2.name, table2.total, 
     COALESCE(
     (
     SELECT SUM(DATEDIFF(day, table1.fromdate, table1.todate) + 1) 
     FROM table1 
     WHERE table1.personid = table2.personid 
     ), 0) AS [days] 
FROM table2 

Answer 3

我觉得一个GROUP BY查询会更简单：

SELECT table2.Id, table2.name, table2.total, 
SUM(DATEDIFF(day, table1.fromdate, table1.todate)) AS Days 
FROM table1 
left outer join table2 on 
table1.personid = table2.personid 
GROUP BY table2.Id, table2.name, table2.total