PowerBi Append two table with error message "Expression.Error: The field 'xxx' already exists

[EllianHs]

Hi 

I started getting errors this week (3/13/2023) when processing append tables in power query.

The message descrinbes there is a certain field has exist but from my understadning, when appending two tables, there shouldn't

has such limitatioion. Anyone could share some light what might go wrong? 

Ellian

[KGillett]

I came across this error yesterday and couldn't make sense of it.  Very glad to find this post and thank the very clever people that work these things out.

[wdx223_Daniel]

it seems the error comes from those two tables

[artemus]

What is your data source type?

While this is probably a bug with the way the data source does combine, it is probably caused by a different casing between the two columns.

[EllianHs]

The data source is data flow. It actually was acting fine but one day the dataset for the report refresh failed and has the error. If I removed the columns throw out the erros, it will just show the next column giving the errors

[artemus · Accepted solution]

Does adding Table.StopFolding(<<table>>) around both tables still result in an error?

I.e.

Table.Combine({Table.StopFolding(<<table>>), Table.StopFolding(<<table>>)})

Also, what version of Power Bi (or Excel) are you using?

[KNP]

Hi @artemus,

I've stumbled across this while trying to solve this very issue.

I was doing a very simple Table.Combine() with two Dataflows and it was throwing an error that made no sense.

Can you explain this solution and what has changed to cause this to be needed?

Do I need to go and check other Datasets that have this Table.Combine() logic?

Thanks.

[artemus]

If this works it indicates there is a bug in the datasource folding implementation (or less likely the power query engine). This funcation forcable breaks folding and as a result works around the bug.

[KNP]

It did work.

The Datasource is Dataflows using the PowerPlatform.Dataflows() connector in my case.

I wasted 3 hours thinking I was doing something wrong, so was glad to find this post. 

Would love to know what has changed and whether this will potentially break existing Datasets.

[artemus]

I would also like to know, but haven't been able to reporduce this problem.

[EllianHs]

Yes, it works !! :). I have Version: 2.114.864.0 64-bit (February 2023).