具有左外连接的数据聚合

Question

我正在尝试按分支、按周提取一些带有事务计数的数据，这些数据稍后将用于提供一些动态 .Net 图表。

我有一个日历表、一个分支表和一个事务表。

这是我的数据库信息（仅包括相关列）：

分支表：

ID (int), Branch (varchar)

日历表：

Date (datetime), WeekOfYear(int)

交易表：

Date (datetime), Branch (int), TransactionCount(int)

所以，我想做如下的事情：

Select b.Branch, c.WeekOfYear, sum(TransactionCount)
FROM BranchTable b
LEFT OUTER JOIN TransactionTable t
    on t.Branch = b.ID
JOIN Calendar c
    on t.Date = c.Date
WHERE YEAR(c.Date) = @Year // (SP accepts this parameter)
GROUP BY b.Branch, c.WeekOfYear

现在，EXCEPT 可以在分支一周内没有任何交易时起作用，在这种情况下，该分支在该周返回 NO RECORD。我想要是获得那个分支，那周和总和为“0”。我试过 isnull(sum(TransactionCount), 0) - 但这也没有用。所以我会得到以下信息（为了说明目的，总结一下）：

+--------+------------+-----+
| Branch | WeekOfYear | Sum |
+--------+------------+-----+
|      1 |          1 |  25 |
|      2 |          1 |  37 |
|      3 |          1 |  19 |
|      4 |          1 |   0 |  //THIS RECORD DOES NOT GET RETURNED, BUT I NEED IT!
|      1 |          2 |  64 |
|      2 |          2 |  34 |
|      3 |          2 |  53 |
|      4 |          2 |  11 |
+--------+------------+-----+

那么，为什么左外连接不起作用？不应该这样吗

任何帮助将不胜感激。谢谢！

编辑：样本表数据：

Branch表：

+----+---------------+
| ID |    Branch     |
+----+---------------+
|  1 | First Branch  |
|  2 | Second Branch |
|  3 | Third Branch  |
|  4 | Fourth Branch |
+----+---------------+

Calendar表：

+------------+------------+
|    Date    | WeekOfYear |
+------------+------------+
| 01/01/2015 |          1 |
| 01/02/2015 |          1 |
+------------+------------+

Transaction表

+------------+--------+--------------+
|    Date    | Branch | Transactions |
+------------+--------+--------------+
| 01/01/2015 |      1 |           12 |
| 01/01/2015 |      1 |            9 |
| 01/01/2015 |      2 |            4 |
| 01/01/2015 |      2 |            2 |
| 01/01/2015 |      2 |           23 |
| 01/01/2015 |      3 |           42 |
| 01/01/2015 |      3 |           19 |
| 01/01/2015 |      3 |            7 |
+------------+--------+--------------+

Answer 1

如果您想返回一个包含每个分支和每周的查询，那么您需要首先创建一个完整的列表，然后对事务使用 LEFT JOIN 来获取计数。代码将类似于：

select bc.Branch, 
   bc.WeekOfYear, 
   TotalTransaction = coalesce(sum(t.TransactionCount), 0)
from
(
  select b.id, b.branch, c.WeekOfYear, c.date
  from branch b
  cross join Calendar c
  -- if you want to limit the number of rows returned use a WHERE to limit the weeks
  -- so far in the year or using the date column
  WHERE c.date <= getdate()
   and YEAR(c.Date) = @Year // (SP accepts this parameter)
) bc
left join TransactionTable t
  on t.Date = bc.Date
  and bc.id = t.branch
GROUP BY bc.Branch, bc.WeekOfYear

See Demo

此代码将在您的子查询中创建包含每个日期的每个分支的完整列表。获得此列表后，您可以加入交易以获取总交易计数，并且您可以根据需要返回每个日期。

Answer 2

在您引入交易之前引入日历：

SELECT b.Branch, c.WeekOfYear, sum(TransactionCount)
FROM BranchTable b 
INNER JOIN CalendarTable c ON YEAR(c.Date) = @Year
LEFT JOIN TransactionTable t ON t.Branch = b.ID AND t.Date = c.Date
GROUP BY b.Branch, c.WeekOfYear
ORDER BY c.WeekOfYear, b.Branch