Ambiguity Error Managing Relationships in data model

Hi Emma_ ,

To avoid many-to-many relationships in your Power BI model, you should restructure into a clean star schema: treat PortfolioFacts as the fact table, connect it to dimension tables (Customer, Product, Advisor, Date, Segment), and use bridge tables where multiple keys overlap. The Customers table can act as a slowly changing dimension (SCD) with valid_from/valid_to, but it should not directly create ambiguous paths—use surrogate keys or bridge tables to manage history.

Recommendation Pattern in PowerBI/Fabric:-

• Star Schema: Always aim for fact in center, dimensions around.

• Role-Playing Date Dimensions: Use multiple relationships from Date to PortfolioFacts (coverage_from, coverage_to, contract_start, contract_end).

• Bridge Tables for Many-to-Many: Cleanest way to resolve ambiguous paths.

• Inactive Relationships + USERELATIONSHIP: Keep only one active relationship per dimension, activate others in DAX when needed.

• Service Accounts for Connections: In Fabric, use service accounts for pipeline/dataflow connections to avoid dependency on individual users (ties back to your earlier consultant issue).

Avoiding Many-to-Many Relationships
Bridge Tables:

Example: If customers can belong to multiple segments, create a CustomerSegmentBridge with unique combinations of customer_id and segment_id.

Connect bridge - Customers and bridge → Segments.

Z-Items Approach (Power Query):

Create a unified “entity list” table (e.g., all unique products or contracts) and connect both fact tables to it. This eliminates direct many-to-many joins.

One-Way Filters:

Use single-direction relationships unless bidirectional filtering is absolutely necessary.

• Redesign Customers as SCD2 with surrogate keys.

• Use PortfolioFacts as the single fact table.

• Introduce bridge tables for segments and multi-valued attributes.

• Apply role-playing date dimensions for contract/portfolio dates.

• Keep relationships single-direction and activate alternates in DAX when needed

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Thank You

Sunita