Cassandra Query Language (CQL) Quickstart

Interested in getting started with Cassandra? Follow these instructions.

  1. Get Apache Cassandra using docker

    You’ll need to have Docker Desktop for Mac, Docker Desktop for Windows, or similar software installed on your computer.

    Apache Cassandra is also available as a tarball or package download.

    docker pull cassandra:latest
  2. Start Cassandra

    A Docker network allows us to access the container’s ports without exposing them on the host.

    docker network create cassandra
    
    docker run --rm -d --name cassandra --hostname cassandra --network cassandra cassandra
  3. Create files

    The Cassandra Query Language (CQL) is very similar to SQL but suited for the JOINless structure of Cassandra.

    Create a file named data.cql and paste the following CQL script in it. This script will create a keyspace, the layer at which Cassandra replicates its data, a table to hold the data, and insert some data into that table:

    -- Create a keyspace
    CREATE KEYSPACE IF NOT EXISTS store WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : '1' };
    
    -- Create a table
    CREATE TABLE IF NOT EXISTS store.shopping_cart (
    userid text PRIMARY KEY,
    item_count int,
    last_update_timestamp timestamp
    );
    
    -- Insert some data
    INSERT INTO store.shopping_cart
    (userid, item_count, last_update_timestamp)
    VALUES ('9876', 2, toTimeStamp(now()));
    INSERT INTO store.shopping_cart
    (userid, item_count, last_update_timestamp)
    VALUES ('1234', 5, toTimeStamp(now()));
    
    docker run --rm --network cassandra -v "$(pwd)/data.cql:/scripts/data.cql" \
     -e CQLSH_HOST=cassandra -e CQLSH_PORT=9042 -e CQLVERSION=3.4.6 nuvo/docker-cqlsh
  4. Load data with cqlsh

    The CQL shell, or cqlsh, is one tool to use in interacting with the database. We’ll use it to load some data into the database using the script you just saved.

    docker run --rm --network cassandra \
    -v "$(pwd)/data.cql:/scripts/data.cql" \
    -e CQLSH_HOST=cassandra -e CQLSH_PORT=9042 \
    -e CQLVERSION=3.4.5 nuvo/docker-cqlsh 

    The cassandra server itself (the first docker run command you ran) takes a few seconds to start up. The above command will throw an error if the server hasn’t finished its init sequence yet, so give it a few seconds to spin up.

  5. Using interactive cqlsh

    Much like an SQL shell, you can also of course use CQLSH to run CQL commands interactively.

    docker run --rm -it --network cassandra \
    nuvo/docker-cqlsh cqlsh cassandra 9042 \ 
    --cqlversion='3.4.5'

    This should get you a prompt like the following:

    Connected to Test Cluster at cassandra:9042.
    [cqlsh 5.0.1 | Cassandra 4.0.4 | CQL spec 3.4.5 | Native protocol v5]
    Use HELP for help.
    cqlsh>
  6. Read some data

     SELECT * FROM store.shopping_cart;
  7. Write some more data

     INSERT INTO store.shopping_cart (userid, item_count) VALUES ('4567', 20);
  8. Clean up

    docker kill cassandra
    docker network rm cassandra 

CONGRATULATIONS!

Hey, that wasn’t so hard, was it?

To learn more, we suggest the following next steps:

  • Read through the Cassandra structure to learn main concepts and how Cassandra works at a high level.

  • Browse through the Case Studies to learn how other users in our worldwide community are getting value out of Cassandra.

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