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naninamu's avatar
naninamu
Helper IV
1 year ago

Left outer Join - but only selected columns from both tables

Hi - I feel this should be easy but I can't work it out.   I have table A - it has let's say 50 columns, it's quite big. I have table B - let's say it also has 50 columns.   I need to merge thes...
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naninamu's avatar
naninamu
Helper IV
1 year ago

Hi PwerQueryKees Honestly I don't really know. It was just something I read that a reference would still hit the table twice, but upon doing more reading I'm seeing contradictions.

 

Which of these approaches would you recommend from a performance point of view:

 

a) Merge Table A with Table B into a new table, remove unwanted columns

b) Duplicate Table A, merge with table B, remove unwanted columns

c) Reference Table A, merge with table B, remove unwanted columns

d) Create a calculated table in DAX and perform the merge in DAX in PBI

 

I have done Option a). I feel this is similar to Option c), as in due to the fact that I am merging Table A to create a new table, it is using all the steps Table A needed to get to that point.

 

I also tried Option d, which worked until I came to buld my chart, and it wouldn't accept anything in the Y axis field. No ideal why, obviously a problem with my data types.

 

Thanks in advance!

 

 

Anonymous's avatar
Anonymous
Not applicable
1 year ago

Hi

Thanks for the solutions everyone offered, and i want to offer some more information foe user to refer to.

hello naninamu , you can consider to select the columns you need in table A, create a new query.

let
  source=Table.SelectColumns(TableA,.....)
in 
Source

Then use this new table to merge with table b

 

Best Regards!

Yolo Zhu

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