PowerBI Natural Left outer join issues with deleted rows in right table

问题

I have two tables.

1) Table 1 : 1 column with date value
2) Table 2 : 2 columns : Date column + business value column

I am trying to use DAX in PowerBI to create a new table using a left outer join to fill missing dates in my second table.

First table :

| Date       |  
| 2015-05-01 |
| 2015-06-01 |
| 2015-07-01 |       
| 2015-08-01 |

Second table :

| Date       | Value    | 
| -----------|--------- |
| 2015-05-01 |        5 |    
| 2015-05-01 |        5 |    
| 2015-06-01 |        6 |    
| 2015-07-01 |        7 |

DAX code to create new table :

Table = 
var table4=
SELECTCOLUMNS(Table1, "Date", Table1[Date]&"")
var table5=
SELECTCOLUMNS(Table2,"value", Table2[value],"Date", Table2[Date]&"")
return
NATURALLEFTOUTERJOIN(table4,table5)

This is returning :

| Date       | Value    | 
| -----------|--------- |
| 2015-05-01 |        5 |    
| 2015-06-01 |        6 |    
| 2015-07-01 |        7 |    
| 2015-08-01 |        NA|

But I want:

| Date       | Value    | 
| -----------|--------- |
| 2015-05-01 |        5 |    
| 2015-05-01 |        5 |    
| 2015-06-01 |        6 |    
| 2015-07-01 |        7 |    
| 2015-08-01 |       NA |

I am not sure why it is removing the second value of

| 2015-05-01      5|

I need the two values for the month of may to remain in the table. Any ideas ? thanks a lot

回答1:

I have contacted Microsoft development team in August, 2019 (via Marco Russo at SQLBI); they confirmed that this behavior was caused by a bug, and promised to fix it in the upcoming releases.

I have tested November, 2019 release of Power BI Desktop and confirm that the bug is indeed fixed.

My test code:

T1 = DATATABLE("Date", INTEGER, {{1}, {2}, {3}, {4}})

T2 = DATATABLE( "Date", INTEGER, "Value", INTEGER, {{1, 5}, {1,5}, {2, 6}, {3, 7}})

Test = 
  VAR T3 = SELECTCOLUMNS(T1, "Date", T1[Date]*1)
  VAR T4 = SELECTCOLUMNS(T2, "Date", T2[Date]*1, "Value", T2[Value])
RETURN 
  NATURALLEFTOUTERJOIN(T3, T4)

Results:

回答2:

As documented: https://docs.microsoft.com/en-us/dax/naturalinnerjoin-function-dax

It joins on the natural columns the rows which matches both and then adds extra columns.

You need to ask yourself why you need this row in your data because when your model is correct, Power-Bi will do the work for you. In your situation you would generate one extra row for each date where a value does not exist, do you need this?

I created your use case and made the correct model:

next I created a table with dates and values and selected on Date: Select values with no date:

It is just how you want to present your data.. I do a summary over the values which fall on the same date..

来源：https://stackoverflow.com/questions/56590141/powerbi-natural-left-outer-join-issues-with-deleted-rows-in-right-table

标签

left-join

powerbi

dax