Creating a new column according to reference table - powerbi

Question

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I am relatively new to PowerBI and I was wondering if someone would be able to help with something I am stuck on. I have the following table (ProductDate) with information in the format below:
Product number
Date
Day of week
5JR38
16 September 2022
Friday
5JR38
17 September 2022
Saturday
5JR38
18 September 2022
Sunday
7QP13
12 September 2022
Monday
7QP13
13 September 2022
Tuesday
7QP13
14 September 2022
Wednesday
7QP13
15 September 2022
Thursday
7QP13
16 September 2022
Friday
7QP13
17 September 2022
Saturday
7QP13
18 September 2022
Sunday
​
I also have another table (ProductStock) with the number of stock available for a specific day of the week range:
Product number
Day ref
Stock
5JR38
FriO
20
5JR38
WEnd
65
7QP13
MFriO
7
7QP13
MidWeek
13
7QP13
WEnd
18
​
The Day ref column in the table above refers to a range of dates which are stored in a separate table (DayReference) as follows:
Day ref
Day of the week
FriO
Friday
MFriO
Monday
MFriO
Friday
WEnd
Saturday
WEnd
Sunday
MidWeek
Tuesday
MidWeek
Wednesday
MidWeek
Thursday
​
The 'Day ref' column in the ProductStock table does not overlap (i.e. for a 'Product Number' there is no 'Day ref' which would refer to a day of the week twice).
What I am trying to do is create a new column using DAX in the first table (ProductDate) with the 'Day ref' populated from the ProductStock tablewith their corresponding day of the week. The expected result should be something like this:
Product number
Date
Day of week
Relevant Day ref
5JR38
16 September 2022
Friday
FriO
5JR38
17 September 2022
Saturday
WEnd
5JR38
18 September 2022
Sunday
WEnd
7QP13
12 September 2022
Monday
MFriO
7QP13
13 September 2022
Tuesday
MidWeek
7QP13
14 September 2022
Wednesday
MidWeek
7QP13
15 September 2022
Thursday
MidWeek
7QP13
16 September 2022
Friday
MFriO
7QP13
17 September 2022
Saturday
WEnd
7QP13
18 September 2022
Sunday
WEnd
I don't really want to create a many-to-many relationship between those tables and would prefer if I add a new column as shown above. Any help or guidance will be much appreciated.
​
Thank you

Answer 1

You can achieve this in the Advanced Query Editor. Just open the Advance Editor for table ProductDate and try to incorporate this below code there-
let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMvUKMrZQ0lEyNFMITi0oSc1NSi1SMDIwMgKKuRVlpiRWKsXqICkzx1QWnFhSWoSh0AKLwtI8mDLzwABDY5AyI0xlvvmYyowxlYWUphZjqDPBVBeempKHRaUpFhMzSoswFeIPGLgyQgEDV4gnYGIB", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Product number" = _t, Date = _t, #"Day of week" = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Product number", type text}, {"Date", type date}, {"Day of week", type text}}),
//--------------------------
//New steps started from here
//---------------------------
#"Merged Queries" = Table.NestedJoin(#"Changed Type", {"Day of week"}, DayReference, {"Day of the week"}, "DayReference", JoinKind.LeftOuter),
#"Expanded DayReference" = Table.ExpandTableColumn(#"Merged Queries", "DayReference", {"Day ref"}, {"DayReference.Day ref"}),
#"Merged Queries1" = Table.NestedJoin(#"Expanded DayReference", {"Product number", "DayReference.Day ref"}, ProductStock, {"Product number", "Day ref"}, "ProductStock", JoinKind.Inner),
#"Expanded ProductStock" = Table.ExpandTableColumn(#"Merged Queries1", "ProductStock", {"Day ref"}, {"ProductStock.Day ref"}),
#"Removed Columns" = Table.RemoveColumns(#"Expanded ProductStock",{"DayReference.Day ref"}),
#"Renamed Columns" = Table.RenameColumns(#"Removed Columns",{{"ProductStock.Day ref", "Relevant Day ref"}}),
#"Sorted Rows" = Table.Sort(#"Renamed Columns",{{"Product number", Order.Ascending}, {"Date", Order.Ascending}})
in
#"Sorted Rows"
Here is the output-