Forum Discussion

Helper III

2 years ago

million-dollar question - Non-Optimal SQL Queries for Many-to-Many Relationships

Hello,

Power BI Direct Query on GCP Views Generates Non-Optimal SQL Queries for Many-to-Many Relationships

The problem is that it makes a kind of cross join on NULLs.
The following article describes a similar case in detail : https://cbailiss.wordpress.com/2022/09/03/power-bi-nullable-column-merge-join-problems/
How to hack this problem?

Best regards

Tips and Tricks

13 Replies

lbendlin
Super User
2 years ago
Don't have nulls in your join columns?

Note that DAX Studio shows you the issue clearly in the RI column.
- hi_world
  Helper III
  2 years ago
  Hi
  Thank you for you response lbendlin
  No, there is no null value in my columns.
  
  There is nothing showing in RI column :
  
  if you have other ideas I'm interested
  Thank you for your help
  Best regards
  - lbendlin
    Super User
    2 years ago
    What's the cardinality of your join columns?
hi_world
Helper III
2 years ago
the problem still remains valid. it's strange that we don't have a workaround
- lbendlin
  Super User
  2 years ago
  Have you reduced the cardinality of the join columns?
  - hi_world
    Helper III
    2 years ago
    This is part of the technical-functional specifications, and I cannot change it. Therefore, I am looking for a solution without reducing the cardinality.