What is many-to-many relationship?

< 1 min read

Many-to-many means multiple records in one table relate to multiple records in another table.
For example, students enrolled in multiple courses and each course has many students.
In analytics, this often happens between two dimension-like tables.
In one project, Products and Promotions had many-to-many mapping.
It caused duplicate sales totals in Power BI visuals.
We solved it using a bridge table to control the relationship.
Many-to-many makes filter behavior complex and harder to validate.
It also impacts performance and aggregation accuracy.
So we usually avoid it unless business logic truly requires it.

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