Table of Contents

Hide Foreign Key Columns

  • 2026-01-09
  • Morten Lønskov

Overview

This best practice rule identifies foreign key columns (many-side of relationships) that are visible to end users. Foreign keys should be hidden because they serve only as relationship connectors and provide no analytical value when displayed.

  • Category: Formatting

  • Severity: Medium (2)

Applies To

  • Data Columns
  • Calculated Columns
  • Calculated Table Columns

Why This Matters

Visible foreign key columns create unnecessary clutter:

  • User confusion: Foreign keys look like useful data but duplicate dimension attributes
  • Redundant fields: Users see both the key and the related dimension attributes
  • Larger field lists: More objects to scroll through finding relevant fields
  • Incorrect usage: Users may group by keys instead of proper dimension attributes
  • Poor visualizations: Charts showing key values instead of descriptive names

Foreign keys exist only to create relationships between tables. Once relationships are established, users should work with dimension attributes, not the foreign keys themselves.

When This Rule Triggers

The rule triggers when a column is:

  1. Used as the "from" column in a relationship (many-side)
  2. The relationship has many cardinality on the from-side
  3. The column is visible (IsHidden = false)
UsedInRelationships.Any(FromColumn.Name == current.Name and FromCardinality == "Many")
and
IsHidden == false

How to Fix

Automatic Fix

This rule includes an automatic fix:

IsHidden = true

To apply:

  1. In the Best Practice Analyzer select flagged foreign key columns
  2. Click Apply Fix

Manual Fix

  1. In TOM Explorer, locate the foreign key column
  2. In Properties pane, set IsHidden to true
  3. Save changes

Common Causes

Cause 1: Incomplete Model Setup

Foreign keys remain visible after creating relationships.

Cause 2: Bulk Import

Tables imported without post-processing to hide foreign keys.

Cause 3: Legacy Models

Older models where foreign key hiding wasn't enforced.

Example

Before Fix

Sales Table Fields (visible):
  - OrderDate
  - CustomerKey  ← Foreign key (should be hidden)
  - ProductKey   ← Foreign key (should be hidden)
  - SalesAmount
  - Quantity

User experience: Field list is cluttered. Users might mistakenly use Sales[CustomerKey] instead of Customer[CustomerName].

After Fix

Sales Table Fields (visible):
  - OrderDate
  - SalesAmount
  - Quantity

User experience: Clean field list. Users naturally use dimension attributes, relationship filtering works automatically.

Compatibility Level

This rule applies to models with compatibility level 1200 and higher.