Merge queries painfully slow

Question

Hello,&nbsp;I am writing a new report in Power BI that requires me to merge two tables/queries together which I have done via the merge as new function.&nbsp;When I do a refresh the data the standard tables load rapidly but when it comes to the merge query, it sits for a few minutes "waiting for dsn...". The image below shows what I am loading which isn't a large amount of data. The first four queries load in 8 seconds but the merge took 5 minutes before completing.&nbsp;I have spent the weekend trying to figure this out and have deselected "Allow data preview to download in the background", this being a common thing to do to improve performance.&nbsp;Does anyone know why the merge is reducing the refresh to a crawl?&nbsp;

tex628 · Answer

What is the dataformat on the columns that you are using for your merge?

kenhardwick · Answer

Currently, the tables are still in their original formats within our ERP system so will be various formats.

tex628 · Answer

But I mean you're doing the merge in power query right?&nbsp;

kenhardwick · Answer

Thats right.&nbsp;

tex628 · Answer

In that case you are using 2 or more columns to perform that merge. What I'm interested in is which datatype these columns have prior to the merge, as that can greatly affect the performance. :-)

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Merge queries painfully slow

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