5. b) Schema Part 2: Linked Table, concatenation & constellation model

Introduction

This tutorial provides a comprehensive guide on the concepts of concatenation, constellation models, and linked tables in Qlik Sense, as discussed in the video "5. b) Schema Part 2: Linked Table, concatenation & constellation model" by Qlik2Express. Understanding these concepts is essential for effectively modeling data in Qlik Sense, allowing for more efficient data analysis and visualization.

Step 1: Understanding Concatenation in Qlik Sense

Concatenation in Qlik Sense allows you to combine multiple tables with similar structures into one unified table. This simplifies data handling and analysis.

How to Implement Concatenation

• Identify tables with similar fields or structures.
• Use the Concatenate keyword in your script.
• Example script for concatenation:

  Table1:
  LOAD Field1, Field2, Field3
  FROM DataSource1;
  
  Concatenate(Table1)
  LOAD Field1, Field2, Field3
  FROM DataSource2;
  

• Ensure that the field names match for successful concatenation.

Practical Tips

• Avoid concatenating tables with different field names unless intended, as this can lead to data inconsistencies.
• Use the Drop command to remove unnecessary tables after concatenation to keep your data model clean.

Step 2: Exploring the Constellation Model

The constellation model is a schema design that organizes data into facts and dimensions, allowing for complex queries and analysis.

Key Features of the Constellation Model

• Fact Tables: Central tables storing quantitative data (e.g., sales figures).
• Dimension Tables: Tables containing descriptive attributes related to facts (e.g., product names, dates).
• Multiple fact tables can share dimension tables, creating a star-like structure.

How to Implement a Constellation Model

• Define your fact tables and identify related dimension tables.
• Load data into each table using the LOAD statement in your script.
• Example script for loading a fact table and its dimensions:

  FactSales:
  LOAD OrderID, ProductID, Quantity, SalesAmount
  FROM SalesData;
  
  DimProducts:
  LOAD ProductID, ProductName, Category
  FROM ProductData;
  

Practical Tips

• Ensure that foreign keys in fact tables correctly reference primary keys in dimension tables for accurate joins.
• Use the Join command if necessary to combine data from different sources.

Step 3: Utilizing Linked Tables

Linked tables in Qlik Sense allow you to create relationships between different tables while maintaining their independence.

How to Create Linked Tables

• Use a common field to link tables.
• Simply load two tables with a shared field, and Qlik will automatically create a relationship.
• Example script for linked tables:

  Customers:
  LOAD CustomerID, CustomerName
  FROM CustomerData;
  
  Orders:
  LOAD OrderID, CustomerID, OrderDate
  FROM OrderData;
  

Common Pitfalls

• Be cautious of circular references, which can lead to ambiguous data relationships.
• Use the Table Viewer in Qlik Sense to visualize your data model and ensure tables are linked correctly.

Conclusion

In this tutorial, we've explored the essential concepts of concatenation, constellation models, and linked tables in Qlik Sense. By implementing these strategies, you can enhance your data modeling capabilities and streamline your analysis process.

Next steps include practicing these techniques in your Qlik Sense environment and exploring additional resources to deepen your understanding of data modeling. For further learning, consider reviewing related videos and documentation.