What issues arise with many-to-many relationships?

< 1 min read

In my project, many-to-many relationships created duplication problems during reporting.
For example, one customer could buy many products and each product could belong to many orders.
When we directly joined the tables, the sales amount got multiplied and totals became incorrect.
It also slowed down Power BI dashboards because joins became heavy and memory usage increased.
Filtering became confusing — slicers showed unexpected counts due to duplicate rows.
Maintaining referential integrity was difficult since no single primary key existed.
Aggregations like SUM and COUNT DISTINCT required extra DAX logic to fix numbers.
To solve it, we introduced a bridge (mapping) table with surrogate keys.
After that, measures calculated correctly and report performance improved significantly.

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