I am stumped.
I am trying to merge two tables into a new table using a LEFT JOIN. Both tables have unique records on each row. When I join the tables, BI creates duplicate rows on some records for no apparent reason. The duplicates are identical in every way.
Can anybody explain this? Is this a bug?
Solved! Go to Solution.
Hi, I was having the same issue, and then I noticed that my second file, from where I was getting the data, had also duplicated figures. That was the problem. After I deleted those duplicates, I clicked on the refresh button, and the problem was solved!
So, I am having the same issue and I just found your post and read it with hope. Although it has been helpful my issue is a little different just a tiny bit.
What I am doing is mergint two tables I am creating with M inside the advance query for one of my tables. In this operation I create two tables by doing a left anti join, that works fine.
I have table A that are all new leases.
I have table B with all terminated leases.
I want a single table C with both, so I need two columns, new lease, terminated lease. All this is fine so far.
I do then a nested join which is a left outer from the new leases to the terminated leases, so im keeping all that is new and just putting a false in those that are not.
The moment i merge is ok, but then when i expand the table is when booom, i get duplicates. The problem i just found is that while im using lease_id as my key to join, there are some that do not have that key because they are not leases, they are owned so it is a different number, and coincidentally those are the duplicated ones.
Any ideas on how to solve it ???
According to your description, I just tested it in my environment. The Merge Queries option works all fine for me without the issue.
I assume the issue is with your data. Could you post your table structure with some sample data which can reproduce the issue? It's better to share a sample pbix file. You can upload it to OneDrive or Dropbox and post the link here. Do mask sensitive data before uploading.
In addition, here is a similar thread for your reference.
I am running the merge again and it is still creating duplicate records from the LHS table. The LHS table has unique rows of data. So I have 183,000 records merged into 187,000 records post join.
I cannot understand why BI would create an exact duplicate of the LHS row in the merged table? Could it possibly be because the primary key is duplicated? I know that this is not scientifically viable however this is the closest I can get to a primary key.
If you haven't already found a solution...
I had a similar issue where LEFT JOIN was creating duplicates, resulting over 1000 rows of data where I should have just 85.
I solved the issue by expanding the relative columns as an aggregate, instead of just an expansion.
Hope that this makes sense.
I am having the same problem with my data. And no, I do not understand your answer to "expand as an aggregate," will you please clarify?
I know this is an old thread, but if someone else is still reading this thread and would like to offer help, I appreciate it!
Thank you for the response. Could you send me an email at email@example.com. I want to talk with you more and share a sample file, but I can't figure out how to upload an excel file here.
I have created a quick sample that I hope helps explain my method. It may not work with your data, but it did fix the issue with mine!
I have two tables, I would like to merge 'Customer Type' with 'Customer Name'.
I would like to merge using the 'ID' column in both, to bring in the 'Cust Type' field from table 'Customer Type' into table 'Customer Name'.
Once successfully merged, I see the below:
I now have the option to expand that column of the merged table to bring in data from the 'Customer Type' table. But this is where I choose to Aggregate a field rather than expand. You may require a different aggregate measure other than median, dependant on data type:
The result from my data is below:
Please also see sample.pbix file which I hope can help you with your issue.
The LEFT JOIN table Merge is creating duplicate records from the LHS table.
I understand what a LEFT JOIN is.
My LHS table only has unique rows. Why is PowerBI creating duplicate records? These are 100% identical in every respect.
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