Replacing missing values based on two columns

[MiltonKeynes]

Hello everyone!

I'm having trouble preparing my data using Power Query in Power BI. I have a dataset that has the following columns: CustomerID, Street Name, Zip Code and Location Code. Location Code has some missing values, but I am able to fill in some of those by merging another query (customer info). Still, I am left with some missing values. In Excel I solved the problem by looking up street name and zip code, and returning corresponding location code (location code is based on this pair).

However, I am a literal noob in Power Query M and, even though I have given this a lot of thought, have not been able to solve the problem. Even though the number of missing values is not that significant, I would prefer not losing data in this case.

My data looks something like this:

CustomerID	Street name	Zip Code	Location code
123	Street 1	123	5000
456	Street 2	456	5002
789	Street 1	123
987	Street 3	987	5003
654	Street 3	987

Obviously, the end result should look like this:

CustomerID	Street name	Zip Code	Location code
123	Street 1	123	5000
456	Street 2	456	5002
789	Street 1	123	5000
987	Street 3	987	5003
654	Street 3	987	5003

I would appreciate any help and suggestions. I am not even sure if this is possible or practical in the first place.

[HotChilli · Accepted solution]

In Power Query:

Duplicate the query

Remove the Customer and Street Name columns.

Filter out the null entries in Location Code column (using the dropdown in the column heading)

This leaves you a kind of master table which matches Zip codes with Locations.

Using 'Merge Queries->Merge as New'

Merge the original and duplicated queries using an Inner Join on the Zip Code.

This gets you a table like this

Expand the column with 'Table' in each row (using the icon in the column heading)

You are really only interested in the new Location Code column. It should be fully populated.

Tidy up your data ( by Removing the old Location Code column)

[MiltonKeynes]

I got it working, thank you very much!

Apologies for the elementary question.

[HotChilli]

Don't worry. It's not an elementary question