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[英]Add a column in a table visual by comparing two columns from different power query tables and then possibly apply a filter (Power BI)
[英]Add column of previous values from table of tables in Power BI / Power Query
在此處尋找Max Zelensky解決方案的后續措施。 假設原始示例具有一個[Date]字段,我試圖再上一層,並添加一列以顯示先前的[Date]值
Per Max,我創建了表格表:
AddedCustom = Table.AddColumn(GroupedRows, "Custom", each Table.AddIndexColumn([tmp],"Occurrence", 1,1) type table)
創建了第二個索引:
SecondIndex= Table.AddColumn(AddedCustom, "Custom.2", each Table.AddIndexColumn([Custom],"Occurance.2", 0,1), type table)
我已經成功添加了引用當前[日期]行的列:
CurrentDate= Table.AddColumn(SecondIndex, "Date.2", each Table.AddColumn([Custom.2],"Date.2", each [Date]), type table)
但是,當我嘗試引用任一索引列(甚至只是放入{0})時,新字段也會出錯。 我可以肯定地說我在表的列中引用表中的行的語法中缺少一些東西,但是我只是不確定如何到達那里-我嘗試過的一些例子沒有成功:
PriorDate= Table.AddColumn(SecondIndex, "PriorDate", each Table.AddColumn([Custom.2],"Prior Date", each {0}[Date]), type table)
-只是看看我是否可以返回第一行的值
PriorDate= Table.AddColumn(SecondIndex, "PriorDate", each Table.AddColumn([Custom.2],"Prior Date", each {[Occurance.2]}[Date]), type table)
-不起作用用於[Occurance]或[Occurance.2]
PriorDate= Table.AddColumn(SecondIndex, "PriorDate", each Table.AddColumn([Custom.2],"Prior Date", each {[Occurance]-1}[Date]), type table)
PriorDate= Table.AddColumn(SecondIndex, "PriorDate", each Table.AddColumn([Custom.2],"Prior Date", each [Custom.2]{0}[Date]), type table)
PriorDate= Table.AddColumn(SecondIndex, "PriorDate", each Table.AddColumn([Custom.2],"Prior Date", each Table.SelectColums([Custom.2],[Date])), type table)
另外,有人可以為我提供有關優化#Tables,{Lists},[Records]等語法和機制的良好參考。我會很感激(我已經讀過Ken Puls的書的第20章幾次,但是還沒有完全停滯)。 提前致謝!
| Name | Date | Occurance | Prior Date (Desired) |
|------|----------|-----------|----------------------|
| A | 1/1/2019 | 1 | null/error |
| A | 3/1/2019 | 2 | 1/1/2019 |
| B | 2/1/2019 | 1 | null/error |
| A | 4/1/2019 | 3 | 3/1/2019 |
| B | 5/1/2019 | 2 | 2/1/2019 |
與這里的答案類似,您可以添加兩個,而不是僅添加一個索引,一個從0
開始,一個從1
開始,我們通過執行自合並來計算前一行。
let
Source = Table.FromRows({{"A",#date(2019,1,1)},{"A",#date(2019,1,3)},{"B",#date(2019,1,2)},{"A",#date(2019,1,4)},{"B",#date(2019,1,5)}}, {"Name", "Date"}),
ChangeTypes = Table.TransformColumnTypes(Source,{{"Name", type text}, {"Date", type date}}),
GroupByName = Table.Group(ChangeTypes, {"Name"}, {{"tmp", each _, type table}}),
AddIndices = Table.AddColumn(GroupByName, "Custom", each Table.AddIndexColumn(Table.AddIndexColumn([tmp],"Occurrence", 1,1),"Prev",0,1)),
ExpandTables = Table.ExpandTableColumn(AddIndices, "Custom", {"Date", "Occurrence", "Prev"}, {"Date", "Occurrence", "Prev"}),
SelfMerge = Table.NestedJoin(ExpandTables,{"Name", "Prev"},ExpandTables,{"Name", "Occurrence"},"Expanded Custom",JoinKind.LeftOuter),
ExpandPriorDate = Table.ExpandTableColumn(SelfMerge, "Expanded Custom", {"Date"}, {"Prior Date"}),
RemoveExtraColumns = Table.RemoveColumns(ExpandPriorDate,{"Prev", "tmp"})
in
RemoveExtraColumns
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