Power BI DAX：基于变量筛选器的两个表之间的交叉连接

Question

I have two input tables in my Power BI model.

1. UserPermission
2. Lookup Table

The above two tables are not related.

UserPermission:

'All' corresponds to all the segments in the Lookup Table, ie X,Y,Z.

Lookup Table:

UserPermission[SgmtID] is equivalent to LookupTable[SegmentID].

I need to develop an output table, by CROSS JOINing the UserName column in the UserPermission table, and the Ports column in the Lookup Table.

Desired Output table:

David needs to have all the ports of all the segments in the lookup table (ie X,Y,Z).

John needs to have all the ports of segment X only.

Mike needs to have all the ports of segment Y only.

Jill needs to have all the ports of segments X and Z only.

The difference between David and Jill is that David can access all segments, while Jill can access multiple segments, but not all segments.

The output table is needed for Row Level Security (RLS).

I know to use CROSS JOIN using VALUES, also some variables and filters. But not able to develop a full DAX query, due to lack of expertise.

Can anyone kindly help me with this?

Answer 1

I think the SUMMARIZECOLUMNS function is probably the easiest one to achieve this with if you need to do this in DAX.

Output Table =
FILTER (
    SUMMARIZECOLUMNS (
        UserPermission[UserName],
        LookupTable[Ports],
        LookupTable[SegmentID],
        "SID", VALUES ( UserPermission[SegmentID] )
    ),
    [SID] < 0 || [SID] = [SegmentID]
)

Recommended reading on this powerful function:

https://www.sqlbi.com/articles/introducing-summarizecolumns/

---

Edit: If you rename UserPermissions[SegmentID] to UserPermissions[SgmtID] so that there aren't two columns of the same name when summarizing, then you can write the combined table as follows and avoid the issue you mentioned in the comments:

Output Table =
FILTER (
    SUMMARIZECOLUMNS (
        UserPermission[UserName],
        UserPermission[SgmtID],
        LookupTable[Ports],
        LookupTable[SegmentID]
    ),
    [SgmtID] < 0 || [SegmentID] = [SgmtID]
)