Create calculated table from two tables

[EnderWiggin]

Hi All,

I would like to create a measure which shows top3 users by name based on their summarized activity values from 'User table' and 'User Activity table'. The filter connection between the tables is 'User table' 1 - many 'User activity table'

The measure result should be a calcualted tabe with two columns: User table [Name], and sum of [Quantity] from User Activity table.

 I tried to do it with CALCULATEDTABLE, TOPN and ADDCOLUMN functions, but I can not figure out the correct measure definition. Could you help me to solve this? Thank you very much!

[EnderWiggin]

@Greg_Deckler thank you very much for your detailed and clear solution, this is what I wanted.  

[Greg_Deckler · Accepted solution]

@EnderWiggin Try below. PBIX is attached below signature.

Username Sum Quantity Top 3 = 
    VAR __BaseTable = 
        SUMMARIZE(
            'User Activity Table',
            [UserId],
            "Sum Quantity", SUM('User Activity Table'[Quantity])
        )
    VAR __Table = 
        ADDCOLUMNS(
            __BaseTable,
            "Username", MAXX(FILTER('User Table', [Id] = [UserId]),[Name]),
            "Rank", RANKX(__BaseTable, [Sum Quantity],,DESC)
        )
    VAR __Result =
        SELECTCOLUMNS(
            FILTER(__Table, [Rank] <= 3),
            "Username", [Username],
            "Sum Quantity", [Sum Quantity]
        )
RETURN
    __Result