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layout: category_index title: “Cassandra Query Language” description: “Master the Cassandra Query Language (CQL). Learn schema design, efficient querying patterns, and complex data types like Collections and UDTs.” category: “03 Cassandra Query Language” permalink: /cassandra/03-cql/ order: 3 toc: true

keywords: [Jules, Technical Documentation]—

Cassandra Query Language (CQL)

Welcome to the heart of Cassandra development. CQL is your interface to the database. While it resembles SQL, it forces you to think in terms of distributed systems constraints. This module will teach you how to model data for scale, not just for correctness.

Module Contents

1. Keyspaces & Tables

Learn why a schema is actually a deployment strategy. Master Replication Factors, Network Topology, and the critical difference between Partition Keys and Clustering Keys. Interactive Demo

2. Select, Insert, Update

Understand the write path vs read path. Learn the “Golden Rule” of querying (always provide the partition key) and why ALLOW FILTERING is a production killer. Interactive Demo

3. Collections & UDTs

Go beyond simple types. Learn how to use Sets, Lists, Maps, and User Defined Types (UDTs) to store complex data without joins. Master the frozen keyword. Interactive Demo

Review & Cheat Sheet

Test your knowledge with interactive flashcards and grab a quick-reference cheat sheet for CQL commands.