How to avoid NULL check in JOIN condition in Tableau

I am trying to change backend DB for Tableau dashboard. Tableau is generating JOIN SQLs with conditions such as: ON a.col1 = b.col2 OR (a.col1 is null and b.col2 is null) Is there a way we can avoid having OR (a.col1 is null and b.col2 is null) condition? I tried ZN and IFNULL with the column name but still such conditions are getting added. The Druid DB supports JOIN only with equality condition and because of IS NULL check , the query is failing. Thanks

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