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March 03, 2025 01:14
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Cassandra Query Language (CQL) Cheatsheet

A quick reference guide to Cassandra Query Language (CQL), covering essential commands, data types, and functions for efficient database management.

Basic CQL Commands

Connecting and Authentication

Connecting to Cassandra:

cqlsh <host> <port> --user=<username> --password=<password>

Example:
cqlsh 127.0.0.1 9042 --user=cassandra --password=cassandra

Without Authentication:

cqlsh <host> <port>

Example:
cqlsh 127.0.0.1 9042

Keyspace Operations

Create Keyspace:

CREATE KEYSPACE <keyspace_name> WITH REPLICATION = { 'class' : '<replication_strategy>', 'replication_factor' : <number> };

Example:
CREATE KEYSPACE my_keyspace WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 3 };

Use Keyspace:

USE <keyspace_name>;

Example:
USE my_keyspace;

Alter Keyspace:

ALTER KEYSPACE <keyspace_name> WITH REPLICATION = { 'class' : '<replication_strategy>', 'replication_factor' : <number> };

Example:
ALTER KEYSPACE my_keyspace WITH REPLICATION = { 'class' : 'NetworkTopologyStrategy', 'dc1' : 3, 'dc2' : 2 };

Drop Keyspace:

DROP KEYSPACE <keyspace_name>;

Example:
DROP KEYSPACE my_keyspace;

Table Operations

Create Table:

CREATE TABLE <table_name> (column1_name data_type PRIMARY KEY, column2_name data_type, ...);

Example:
CREATE TABLE users (id UUID PRIMARY KEY, name text, age int);

Alter Table (Add Column):

ALTER TABLE <table_name> ADD <column_name> data_type;

Example:
ALTER TABLE users ADD email text;

Drop Table:

DROP TABLE <table_name>;

Example:
DROP TABLE users;

Truncate Table:

TRUNCATE TABLE <table_name>;

Example:
TRUNCATE TABLE users;

Data Manipulation

Insert Data

INSERT INTO <table_name> (column1, column2, ...) VALUES (value1, value2, ...);

Example:
INSERT INTO users (id, name, age, email) VALUES (UUID(), 'John Doe', 30, '[email protected]');

Select Data

SELECT column1, column2, ... FROM <table_name> WHERE condition;

Example:
SELECT id, name, age FROM users WHERE name = 'John Doe';
SELECT * FROM users WHERE age > 25;

Update Data

UPDATE <table_name> SET column1 = value1, column2 = value2, ... WHERE condition;

Example:
UPDATE users SET age = 31 WHERE id = aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee;

Delete Data

DELETE FROM <table_name> WHERE condition;

Example:
DELETE FROM users WHERE id = aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee;
DELETE age, email FROM users WHERE id = aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee;

Data Types

Common Data Types

text

Variable-length UTF-8 string.

ascii

US-ASCII string.

bigint

64-bit signed long.

blob

Arbitrary sequence of bytes (up to 2GB).

boolean

True or False.

decimal

Variable-precision decimal.

double

64-bit IEEE-754 floating point.

float

32-bit IEEE-754 floating point.

int

32-bit signed integer.

timestamp

Date and time (stored as milliseconds since epoch).

uuid

Type 4 universally unique identifier.

timeuuid

Type 1 time-based universally unique identifier.

inet

IPv4 or IPv6 address.

Advanced CQL Features

Indexes

Creating an Index:

CREATE INDEX IF NOT EXISTS <index_name> ON <table_name> (<column_name>);

Example:
CREATE INDEX IF NOT EXISTS users_name_idx ON users (name);

Dropping an Index:

DROP INDEX IF EXISTS <index_name>;

Example:
DROP INDEX IF EXISTS users_name_idx;

Batch Statements

Executing Multiple Statements Atomically:

BEGIN BATCH statement1; statement2; ... APPLY BATCH;

Example:
BEGIN BATCH INSERT INTO users (id, name, age) VALUES (UUID(), 'Alice', 28); UPDATE users SET age = 29 WHERE name = 'Alice'; APPLY BATCH;

Using Functions

Built-in Functions:

CQL provides various built-in functions for data manipulation.

Examples:
token(partition_key): Returns the token of a partition key.
now(): Returns the current timestamp.
toDate(timestamp): Converts a timestamp to a date.

Example Usage:

SELECT * FROM users WHERE token(id) > token(min_id) AND token(id) <= token(max_id);