Excel Power Query 合并 - 连接两个表，其中公共字段不唯一，仅在一个特定列中没有重复值

Question

我有 2 个表，我正在通过 Excel Power Query 合并加入这些表。我有一个 Hours 表和一个 Parts 表。我在 Task_ID 上使用左外连接来保留 Hours 表中的所有行并添加 Parts 表中的匹配行。这很好，可以从 Parts 表中提取 Part No. 和 Cost 但是因为我的公共字段 (Task_ID) 不是唯一的，所以我得到了预期的重复行，但我不想在 中重复值Sum of Hours 列（使用聚合函数从较早的连接创建）。

我想要的输出是可能的，还是有更好的方法来解决这个问题？

例如，我想获得每个任务每周的总小时数和每个任务每周的总成本

小时

| Week | Task_ID | Sum of Hours |
| ---- |-------- |------------- |
| 01   | ABC#1   | 1            |
| 01   | ABC#2   | 3            |
| 02   | ABC#2   | 3            |

零件

| Task_ID | Part No. | Cost |
| ------- | -------- | ---- |
| ABC#1   | 111      | 10   |
| ABC#1   | 222      | 20   |
| ABC#2   | 111      | 10   |
| ABC#2   | 333      | 30   |
| ABC#2   | 444      | 40   | 

期望的输出

| Week | Task_ID | Sum of Hours | Part No. | Cost |
| ---- | ------- | ------------ | -------- | ---- |
| 01   | ABC#1   | 1            | 111      | 10   |
| 01   | ABC#1   | null         | 222      | 20   |
| 01   | ABC#2   | 3            | 111      | 10   |
| 01   | ABC#2   | null         | 222      | 20   |
| 01   | ABC#2   | null         | 333      | 30   |
| 02   | ABC#2   | 3            | 111      | 10   |
| 02   | ABC#2   | null         | 222      | 20   |
| 02   | ABC#2   | null         | 333      | 30   |

Answer 1

不确定问题中显示的所需输出是否完全正确或仅作为粗略示例。例如，它似乎不包含 Task_ID 为 ABC#2 和 Part No. 为 444 的行，即使 ABC#2 出现在 Hours 表中。

下面的代码应该会为您提供类似于您在预期输出中为 Sum Of Hours 列显示的内容（即，第一次出现的原始值，然后是任何重复出现的 null）。

let
    hours = Table.FromColumns({
        {"01", "01", "02"},
        {"ABC#1", "ABC#2", "ABC#2"},
        {1, 3, 3}
    }, type table [Week = text, Task_ID = text, Sum Of Hours = text]),
    parts = Table.FromColumns({
        {"ABC#1", "ABC#1", "ABC#2", "ABC#2", "ABC#2"},
        {111, 222, 111, 333, 444},
        {10, 20, 10, 30, 40}
    }, type table [Task_ID = text, #"Part No." = text, Cost = text]),
    joined = Table.NestedJoin(hours, "Task_ID", parts, "Task_ID", "_joined", JoinKind.LeftOuter),
    nestedIndex = Table.TransformColumns(joined, {"_joined", each Table.AddIndexColumn(_, "_index"), type table}),
    expanded = Table.ExpandTableColumn(nestedIndex, "_joined", {"Part No.", "Cost", "_index"}),
    madeDuplicatesNull = Table.FromRecords(Table.TransformRows(expanded, each 
        Record.RemoveFields(_, {"_index", "Sum Of Hours"}) 
        & [Sum Of Hours = if [_index] > 0  then null else [Sum Of Hours]]
    ))
in
    madeDuplicatesNull

---

但是，如果这里的目标只是每周计算每个任务的一些数字，您可能可以直接计算数字（必要时删除重复数据）而不扩展行？比如：

let
    hours = Table.FromColumns({
        {"01", "01", "02"},
        {"ABC#1", "ABC#2", "ABC#2"},
        {1, 3, 3}
    }, type table [Week = text, Task_ID = text, Sum Of Hours = text]),
    parts = Table.FromColumns({
        {"ABC#1", "ABC#1", "ABC#2", "ABC#2", "ABC#2"},
        {111, 222, 111, 333, 444},
        {10, 20, 10, 30, 40}
    }, type table [Task_ID = text, #"Part No." = text, Cost = text]),
    joined = Table.NestedJoin(hours, "Task_ID", parts, "Task_ID", "_joined", JoinKind.LeftOuter),
    grouped = Table.Group(joined, {"Week", "Task_ID"}, {
        {"Sum Of Hours", each List.Single([Sum Of Hours]), type number},
        {"Cost", each
            let
                aggregated = Table.AggregateTableColumn(_, "_joined", {{"Cost", List.Sum, "Cost"}}),
                cost = List.Single(aggregated[Cost])
            in cost
        , type number}
    })
in
    grouped