Cassandra Query Language (CQL) Quickstart

Interested in getting started with Cassandra? Follow these instructions.

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
```

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

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

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.

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>

Read some data
```
 SELECT * FROM store.shopping_cart;
```

Write some more data

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

Clean up

docker kill cassandra
docker network rm cassandra

To get a high-level overview of Cassandra, see Cassandra structure.

Cassandra Query Language (CQL) Quickstart

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