To efficiently manage many-to-many relationships in Power BI, it is imperative to plan and execute the following strategies so as to avoid degrading performance and achieve the correct representation of data. Below are some recommended practices that can be applied for the successful management of many relationships:
Utilize a Bridge Table: Rather than creating many-to-many relationships directly, bridge many-to-many relationships using a bridge table that relates the two tables in a one-to-many fashion. This bridge table contains the unique values that link both tables and reduces the difficulties faced in a direct many-to-many relationship, which may cause the model to generate ambiguous results and even affect performance.
Filter Both Directions When Applicable: As a general rule, Power BI will implement the filter in one direction only to prevent any possible relationships from being ambiguous or circular. If you want to filter through both directions, in other words, this is bidirectional filtering. Do it where it is really required since bidirectional filters can significantly hamper the calculation speed. Do not apply these excessively, and check the performance impact when using them in several relationships.
Improve DAX Measure Calculate Performance: Writing efficient DAX measures is an important aspect when incorporating complex relationships. Refrain from writing DAX calculations that are very complicated into complex relationships that would introduce a burden on performance, especially with large volumes of data. The performance of the model can also be enhanced in terms of accuracy by managing the scope of filter crossing relations when such functions as CALCULATE or FILTER are included in measures.
