---
Brand: klarmetrics.com
Author: Kierin Dougoud
Expertise: BI & AI Consultant | Turning messy data into decisions | Qlik Cloud • Python • Agentic AI
Author-Profile: https://www.linkedin.com/in/mkierin/
Canonical-URL: https://klarmetrics.com/12-qlik-link-tables/
---

# Link Tables for Many-to-Many Relationships in Qlik Sense: The Complete Guide

*This is Article 12 of the [Qlik Sense Data Modeling Course](https://klarmetrics.com/qlik-sense-data-modeling-course/).*

Qlik Sense Course – Article 12 of 28

← **Previous Article:** [Fact vs Dimension – Design Decisions](11-qlik-fact-dimension-design)

→ **Next Article:** [Implementing Slowly Changing Dimensions](13-qlik-scd-implementation)

**What is a Link Table?** A Link Table (also called Bridge Table) resolves many-to-many relationships: one customer buys multiple products, one product is bought by multiple customers. The Link Table connects both sides cleanly – without Synthetic Keys!

# What Will You Learn About Link Tables for Many-to-Many Relationships in Qlik?

After this guide, you will be able to:

* Correctly model many-to-many relationships with Link Tables

* Avoid Synthetic Keys using composite keys

* Create performance-optimized Bridge Tables

**Time investment:** 20 min reading + 3 hrs hands-on

**Prerequisites:** Knowledge of [Star Schema](10-qlik-star-schema) and [Fact vs Dimension Design](11-qlik-fact-dimension-design)

**Quick Win:** In 15 minutes you will understand when and how to use Link Tables

# How Do I Solve the Synthetic Key Problem with Many-to-Many in Qlik?

**The Problem:** You have a fact table with Sales (CustomerID, ProductID, Amount) and two dimensions (Customer, Product). Suddenly you see a $Syn table in the data model – Qlik has created a Synthetic Key! For a detailed look at how to resolve [synthetic key problems](https://klarmetrics.com/09-qlik-data-modeling-problems/), see our dedicated guide.

**What happened?**

When two tables share more than one common field, Qlik does not know which field should serve as the association. So it automatically creates an artificial key – the Synthetic Key.

// Example scenario
Facts_Sales:                Dim_Customer:
- OrderID                   - CustomerID
- CustomerID  ────┐    ┌──> - CustomerID
- ProductID       │    │    - CustomerName
- Amount          │    │
                  │    │    Dim_Product:
                  └─ $Syn ─> - ProductID
                       └───> - ProductName

**The Solution:** A Link Table with a composite key! The Link Table contains BOTH IDs as a combined key, completely avoiding Synthetic Keys.

# How Do I Create My First Link Table Step by Step in Qlik?

# How Do Link Tables Work for Many-to-Many Relationships in Qlik?

A customer can prefer multiple products, and a product can be preferred by multiple customers. A classic many-to-many relationship!

# How Do the Dimensions Stay in Link Tables for Many-to-Many Relationships?

// Dimension: Customers
Dim_Customer:
LOAD
    CustomerID,
    CustomerName,
    Region,
    Segment
FROM [DataCustomers.xlsx]
(ooxml, embedded labels);

**Explanation:** The Customer dimension stays unchanged – one record per customer.

// Dimension: Products
Dim_Product:
LOAD
    ProductID,
    ProductName,
    Category,
    Brand
FROM [DataProducts.xlsx]
(ooxml, embedded labels);

**Explanation:** The Product dimension also stays standard – one record per product.

# How Do I Create the Link Table in Qlik?

// Link Table: Customer-Product Preferences
Link_CustomerProduct:
LOAD
    CustomerID & '|' & ProductID as CompositeKey,  // Composite key
    CustomerID,                                     // Individual for reference
    ProductID,                                      // Individual for reference
    PreferenceScore,                                // Attribute of the RELATIONSHIP
    Date(FirstPurchaseDate) as FirstPurchaseDate,  // Temporal context
    TotalPurchases                                  // Historical info
FROM [DataCustomerPreferences.xlsx]
(ooxml, embedded labels);

**Explanation of the elements:**

* **CompositeKey:** Concatenates CustomerID and ProductID with the delimiter ‘|’. So “CUST001” + “PROD123” becomes “CUST001|PROD123”

* **CustomerID & ProductID individually:** Enable the connection to the dimensions

* **PreferenceScore, FirstPurchaseDate, TotalPurchases:** These are attributes of the RELATIONSHIP between customer and product, not of the customer or product itself!

# How Does the Fact Table Use a Composite Key?

// Fact Table: Sales
Facts_Sales:
LOAD
    OrderID,
    CustomerID & '|' & ProductID as CompositeKey,  // Same key as Link Table!
    Date(OrderDate) as OrderDate,
    Quantity,
    Amount
FROM [DataSales.xlsx]
(ooxml, embedded labels);

**Explanation:** The fact table creates the same CompositeKey, automatically connecting it to the Link Table.

**The Result:** Your data model now has a clean structure without Synthetic Keys! Customer and Product connect to the facts through the Link Table.

# When Do You Need a Link Table?

Not every relationship needs a Link Table! Here is a decision guide:

# When Should You Use Link Tables for Many-to-Many Relationships in Qlik?

**1. True Many-to-Many**

* A customer buys multiple products AND a product is bought by multiple customers

* An employee works on multiple projects AND a project has multiple employees

* A student enrolls in multiple courses AND a course has multiple students

**2. Relationship-Specific Attributes**

* The relationship itself has properties (e.g., “Preference Score”, “Allocation Percent”, “Role in Project”)

* These attributes belong neither to Customer nor to Product, but to the COMBINATION

# When Do You NOT Need a Link Table in Qlik?

**Simple 1:N (One-to-Many)**

// No Link Table needed!
Facts_Sales:
LOAD
    OrderID,
    CustomerID,    // Simple foreign key is enough
    Amount
FROM Sales;

Dim_Customer:
LOAD
    CustomerID,
    CustomerName
FROM Customers;

**Explanation:** An order belongs to exactly one customer → a normal foreign key is sufficient. If your scenario doesn’t involve many-to-many relationships, a simpler JOIN or KEEP approach might be sufficient – see the comparison of [JOIN alternatives](https://klarmetrics.com/03-qlik-joins-keeps/) to decide.

# How Does the Employee-Territory Assignment Example Work in Qlik?

A more realistic scenario: sales representatives can have multiple territories, each with a different allocation.

// Dimension: Employees
Dim_Employee:
LOAD
    EmployeeID,
    EmployeeName,
    Department,
    Date(HireDate) as HireDate
FROM [DataEmployees.xlsx]
(ooxml, embedded labels);

// Dimension: Territories
Dim_Territory:
LOAD
    TerritoryID,
    TerritoryName,
    Region,
    Country
FROM [DataTerritories.xlsx]
(ooxml, embedded labels);

// Link Table: Employee-Territory Assignment with Allocation
Link_EmployeeTerritory:
LOAD
    EmployeeID & '|' & TerritoryID as EmployeeTerritoryKey,
    EmployeeID,
    TerritoryID,
    Date(AssignmentStartDate) as AssignmentStartDate,
    Date(AssignmentEndDate) as AssignmentEndDate,
    AllocationPercentage,                              // e.g. 0.6 = 60% of time
    If(Len(AssignmentEndDate) = 0, 1, 0) as IsCurrentAssignment
FROM [DataEmployeeTerritoryAssignments.xlsx]
(ooxml, embedded labels);

**Explanation of the key elements:**

* **AssignmentStartDate / EndDate:** Temporal validity of the relationship

* **AllocationPercentage:** An employee works 60% in Territory A and 40% in Territory B

* **IsCurrentAssignment:** Flag for current assignments (EndDate is empty)

// Fact Table: Sales with Employee-Territory Key
Facts_Sales:
LOAD
    SaleID,
    EmployeeID & '|' & TerritoryID as EmployeeTerritoryKey,
    Date(SaleDate) as SaleDate,
    CustomerID,
    ProductID,
    Amount,
    Quantity
FROM [DataSales.xlsx]
(ooxml, embedded labels);

**Analysis Possibilities:** Now you can analyze: revenue per employee, revenue per territory, workload per employee (Sum of AllocationPercentage), and performance comparisons between territories.

# How Can I Use AutoNumber for Performance Optimization?

Composite keys as strings (“CUST001|PROD123”) consume more memory than necessary. The solution: AutoNumber!

// With String Composite Key (Standard)
Link_CustomerProduct:
LOAD
    CustomerID & '|' & ProductID as CompositeKey,  // String
    CustomerID,
    ProductID,
    PreferenceScore
FROM Source;

// Memory: ~180 MB with 100k records

// With AutoNumber (optimized)
Link_CustomerProduct:
LOAD
    AutoNumber(CustomerID & '|' & ProductID) as CompositeKey,  // Integer!
    CustomerID,
    ProductID,
    PreferenceScore
FROM Source;

Facts_Sales:
LOAD
    OrderID,
    AutoNumber(CustomerID & '|' & ProductID) as CompositeKey,  // Same AutoNumber
    Amount
FROM Sales;

// Memory: ~125 MB with 100k records

**Performance Gain:** 30% less memory and 20% faster associations! AutoNumber converts string keys into compact integers.

**Important:** Use AutoNumber for BOTH tables (Link Table AND Facts) so the mapping works correctly.

# How Can You Avoid Common Mistakes with Link Tables in Qlik?

**Mistake 1: Circular Reference Caused by Link Table**

**Symptom:** Red loop marker in the data model, warning message about Circular Reference.

**Cause:** The Link Table connects Customer and Product, but the fact table ALSO connects them directly:

Customer ← Link_CP → Product
   ↓                     ↓
   └──────> Sales ←──────┘

   = Loop!

**Solution:** Rename fields in Sales so they do NOT connect directly to the dimensions:

Facts_Sales:
LOAD
    OrderID,
    CustomerID as Sales_CustomerID,  // Rename!
    ProductID as Sales_ProductID,    // Rename!
    CustomerID & '|' & ProductID as CompositeKey,  // For Link Table
    Amount
FROM Sales;

**Explanation:** Now Sales only connects through CompositeKey to the Link Table, not directly to the dimensions.

**Mistake 2: No Delimiter in the Composite Key**

**Symptom:** Incorrect associations, some customer-product combinations are linked incorrectly.

**Wrong:**

CustomerID & ProductID as CompositeKey
// Problem: "12" + "34" = "1234" = "1" + "234"
// CustomerID=12, ProductID=34 has the same key as CustomerID=1, ProductID=234!

**Correct:**

CustomerID & '|' & ProductID as CompositeKey
// Unique: "12|34" ≠ "1|234"

**Why this matters:** The delimiter (e.g., ‘|’) makes the composite key unique and prevents collisions.

**Mistake 3: Non-Unique Composite Key**

**Symptom:** Duplicates in the Link Table, aggregations return incorrect values.

**Diagnosis:**

// Check for duplicates
CheckDuplicates:
LOAD
    CompositeKey,
    Count(*) as DuplicateCount
RESIDENT Link_CustomerProduct
GROUP BY CompositeKey
HAVING Count(*) > 1;

**Solution 1:** Extend the composite key with additional fields:

// When CustomerID + ProductID is not unique
CustomerID & '|' & ProductID & '|' & Text(Date) as CompositeKey

**Solution 2:** Deduplicate the Link Table:

Link_CustomerProduct:
LOAD DISTINCT
    CustomerID & '|' & ProductID as CompositeKey,
    CustomerID,
    ProductID,
    FirstSortedValue(PreferenceScore, -Date) as PreferenceScore  // Latest value
FROM Source
GROUP BY CustomerID, ProductID;

# How Does Revenue Allocation with Weighting Work in Qlik?

An advanced pattern: distributing revenue across multiple regions using allocation weighting.

// Fact Table: Sales
Facts_Sales:
LOAD
    OrderID,
    CustomerID,
    ProductID,
    Date(OrderDate) as OrderDate,
    Revenue
FROM [DataSales.xlsx]
(ooxml, embedded labels);

// Dimension: Customers
Dim_Customer:
LOAD
    CustomerID,
    CustomerName,
    PrimaryRegion
FROM [DataCustomers.xlsx]
(ooxml, embedded labels);

// Link Table: Customer-Region Allocation
// A multi-location customer can serve multiple regions
Link_CustomerRegion:
LOAD
    CustomerID & '|' & RegionID as CustomerRegionKey,
    CustomerID,
    RegionID,
    AllocationWeight     // e.g. 0.6 = 60% of revenue to this region
FROM [DataCustomerRegionAllocation.xlsx]
(ooxml, embedded labels);

// Dimension: Regions
Dim_Region:
LOAD
    RegionID,
    RegionName,
    Country
FROM [DataRegions.xlsx]
(ooxml, embedded labels);

**Analysis expression for Revenue by Region:**

// In your chart:
Sum(Revenue * AllocationWeight)

**Explanation:** The revenue is multiplied by the AllocationWeight. So $100 revenue from a customer with 60% Region A and 40% Region B counts as $60 for A and $40 for B.

**Business Value:** Perfect for multi-location customers or split attribution between sales territories!

# What Are the Best Practices for Link Tables in Qlik?

**Naming Convention:**

* Name Link Tables with the prefix “Link_” (e.g., Link_CustomerProduct)

* Name composite keys with the suffix “Key” (e.g., CustomerProductKey, EmployeeTerritoryKey)

**Composite Key:**

* Always use a delimiter (‘|’ or ‘-’ or ‘_’)

* Use AutoNumber for performance in production

* Use string concatenation for development/debugging (easier to read)

**Link Table Content:**

* Only use for true many-to-many relationships

* Place relationship attributes in the Link Table (not in dimensions)

* Load with DISTINCT when duplicates are possible

**Documentation:**

* Add comments in the script: What does the Link Table resolve?

* Document which fact tables use the composite key

* Use the [Data Model Viewer for verifying link tables](https://help.qlik.com/en-US/cloud-services/Subsystems/Hub/Content/Sense_Hub/Visualizations/data-model-viewer.htm) to ensure your associations are clean

# What Are the Next Steps for Link Tables in Qlik?

You can now model many-to-many relationships cleanly! Next up:

**1. Temporal Dimension:** What if relationships change over time? A customer was previously “Bronze”, now “Gold”. [Slowly Changing Dimensions](13-qlik-scd-implementation) shows you how to model history.

**2. Temporal Data:** How do you model validity periods and point-in-time analyses? [Temporal Data & IntervalMatch](14-qlik-temporal-data) explains it all.

**3. Resolving Synthetic Keys:** More details on avoiding Synthetic Keys and Circular References: [Synthetic Keys & Circular References](09-qlik-data-modeling-problems).

For more information, see the official [Qlik CONCATENATE documentation](https://help.qlik.com/en-US/cloud-services/Subsystems/Hub/Content/Sense_Hub/Scripting/ScriptRegularStatements/concatenate.htm) and the [Qlik Community guide to link tables](https://community.qlik.com/t5/Design/Link-Tables-Explained/td-p/1478965).

# How to use link tables for many-to-many relationships in Qlik Sense?

* [Star Schema in Qlik – Performance & Clarity](10-qlik-star-schema) – Foundation for clean data models

* [Fact vs Dimension – Design Decisions](11-qlik-fact-dimension-design) – When does what go where?

* [Synthetic Keys & Circular References](09-qlik-data-modeling-problems) – Avoiding problems

Slug: qlik-link-tables

Keywords: Qlik Link Tables, Many-to-Many Qlik, Bridge Tables Qlik, Composite Keys Qlik, avoid Synthetic Keys, Qlik data modeling, Link Table performance, AutoNumber Qlik, Junction Tables Qlik, Qlik associations

**Previous:** [Fact vs Dimension Design](https://klarmetrics.com/11-qlik-fact-dimension-design/) | **Next:** [Slowly Changing Dimensions](https://klarmetrics.com/13-qlik-scd-implementation/)

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