Learn Mql - 10 Code Examples & CST Typing Practice Test

MongoDB Query Language (MQL) is a rich, expressive, and flexible query language used to interact with MongoDB, a document-oriented NoSQL database. MQL enables data retrieval, manipulation, aggregation, and management of JSON-like documents.

View all 10 Mql code examples →

Basic MQL Queries Basic SQL Queries PostgreSQL Joins Redis Basics MySQL Aggregations SQLite Table Creation Cassandra CQL Queries Neo4j Cypher Basics Elasticsearch DSL Queries InfluxDB Time-Series Queries

Learn MQL with Real Code Examples

Updated Nov 18, 2025

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Code Sample Descriptions

Basic MQL Queries

// Find users aged over 25

db.users.find({ age: { $gt: 25 } })

// Find users, only return name and email

db.users.find({}, { name: 1, email: 1 })

// Aggregation: group by status and count

db.orders.aggregate([
    { $group: { _id: "$status", total: { $sum: 1 } } }
])

Examples of finding documents, projecting fields, and using aggregation in MongoDB.

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Basic SQL Queries

-- Select all users
SELECT * FROM users;

-- Select specific columns
SELECT name, email FROM users;

-- Select with filter
SELECT * FROM users WHERE age > 25;

-- Order results
SELECT * FROM users ORDER BY created_at DESC;

Simple SQL operations: SELECT, WHERE, ORDER BY.

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PostgreSQL Joins

-- Inner Join
SELECT u.name, o.id
FROM users u
INNER JOIN orders o ON u.id = o.user_id;

-- Left Join
SELECT u.name, o.id
FROM users u
LEFT JOIN orders o ON u.id = o.user_id;

-- Right Join
SELECT u.name, o.id
FROM users u
RIGHT JOIN orders o ON u.id = o.user_id;

Examples of INNER JOIN, LEFT JOIN, and RIGHT JOIN in PostgreSQL.

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Redis Basics

# Set and Get
SET user:1 "Alice"
GET user:1

# Hash operations
HSET user:2 name "Bob" age 30
HGETALL user:2

# List operations
LPUSH tasks "task1" "task2"
LRANGE tasks 0 -1

Basic Redis key-value operations.

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MySQL Aggregations

-- Count users
SELECT COUNT(*) FROM users;

-- Average age
SELECT AVG(age) FROM users;

-- Total orders
SELECT SUM(amount) FROM orders;

Aggregations like COUNT, AVG, SUM in MySQL.

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SQLite Table Creation

-- Create table
CREATE TABLE users (
    id INTEGER PRIMARY KEY,
    name TEXT,
    email TEXT
);

-- Insert row
INSERT INTO users (name, email) VALUES ('Alice', 'alice@mail.com');

-- Query
SELECT * FROM users;

Creating tables and inserting rows in SQLite.

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Cassandra CQL Queries

-- Create keyspace
CREATE KEYSPACE shop WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};

-- Use keyspace
USE shop;

-- Create table
CREATE TABLE users (id UUID PRIMARY KEY, name TEXT, age INT);

-- Insert
INSERT INTO users (id, name, age) VALUES (uuid(), 'Alice', 29);

-- Select
SELECT * FROM users;

Basic CQL queries for Cassandra.

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Neo4j Cypher Basics

// Create nodes
CREATE (a:Person {name: "Alice"}), (b:Person {name: "Bob"});

// Create relationship
MATCH (a:Person {name: "Alice"}), (b:Person {name: "Bob"})
CREATE (a)-[:FRIEND]->(b);

// Query
MATCH (p:Person)-[:FRIEND]->(f)
RETURN p.name, f.name;

Basic graph queries using Cypher in Neo4j.

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Elasticsearch DSL Queries

{
    "query": {
        "bool": {
        "must": [
        { "match": {title: "database" } },
        { "range": { "year": { "gte": 2020 } } }
        ]
        }
    }
}

JSON-based query DSL examples in Elasticsearch.

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InfluxDB Time-Series Queries

-- Create measurement
INSERT temperature,location=room1 value=23.5

-- Select with time filter
SELECT value FROM temperature WHERE time > now() - 1h;

-- Aggregate
SELECT MEAN(value) FROM temperature WHERE time > now() - 24h GROUP BY time(1h);

InfluxQL examples for querying time-series data.

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Frequently Asked Questions about Mql

What is Mql?

What are the primary use cases for Mql?

CRUD operations (Create, Read, Update, Delete). Complex querying with filters. Aggregation and reporting. Indexing for performance optimization. Data modeling for NoSQL document storage. ETL and analytics pipelines

What are the strengths of Mql?

Flexible schema design. Powerful aggregation and filtering. High scalability for distributed systems. Wide ecosystem and language drivers. JSON-style document storage aligned with modern applications

What are the limitations of Mql?

Limited transactions (single-document atomicity in MongoDB <4.0). Joins are limited compared to relational databases. Requires careful schema design for performance. Aggregation pipelines can be complex for large datasets

How can I practice Mql typing speed?

CodeSpeedTest offers 10+ real Mql code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.

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Code Sample Descriptions

Basic MQL Queries

// Find users aged over 25

db.users.find({ age: { $gt: 25 } })

// Find users, only return name and email

db.users.find({}, { name: 1, email: 1 })

// Aggregation: group by status and count

db.orders.aggregate([
    { $group: { _id: "$status", total: { $sum: 1 } } }
])

Examples of finding documents, projecting fields, and using aggregation in MongoDB.

Let’s Try →

Basic SQL Queries

-- Select all users
SELECT * FROM users;

-- Select specific columns
SELECT name, email FROM users;

-- Select with filter
SELECT * FROM users WHERE age > 25;

-- Order results
SELECT * FROM users ORDER BY created_at DESC;

Simple SQL operations: SELECT, WHERE, ORDER BY.

Let’s Try →

PostgreSQL Joins

-- Inner Join
SELECT u.name, o.id
FROM users u
INNER JOIN orders o ON u.id = o.user_id;

-- Left Join
SELECT u.name, o.id
FROM users u
LEFT JOIN orders o ON u.id = o.user_id;

-- Right Join
SELECT u.name, o.id
FROM users u
RIGHT JOIN orders o ON u.id = o.user_id;

Examples of INNER JOIN, LEFT JOIN, and RIGHT JOIN in PostgreSQL.

Let’s Try →

Redis Basics

# Set and Get
SET user:1 "Alice"
GET user:1

# Hash operations
HSET user:2 name "Bob" age 30
HGETALL user:2

# List operations
LPUSH tasks "task1" "task2"
LRANGE tasks 0 -1

Basic Redis key-value operations.

Let’s Try →

MySQL Aggregations

-- Count users
SELECT COUNT(*) FROM users;

-- Average age
SELECT AVG(age) FROM users;

-- Total orders
SELECT SUM(amount) FROM orders;

Aggregations like COUNT, AVG, SUM in MySQL.

Let’s Try →

SQLite Table Creation

-- Create table
CREATE TABLE users (
    id INTEGER PRIMARY KEY,
    name TEXT,
    email TEXT
);

-- Insert row
INSERT INTO users (name, email) VALUES ('Alice', 'alice@mail.com');

-- Query
SELECT * FROM users;

Creating tables and inserting rows in SQLite.

Let’s Try →

Cassandra CQL Queries

-- Create keyspace
CREATE KEYSPACE shop WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};

-- Use keyspace
USE shop;

-- Create table
CREATE TABLE users (id UUID PRIMARY KEY, name TEXT, age INT);

-- Insert
INSERT INTO users (id, name, age) VALUES (uuid(), 'Alice', 29);

-- Select
SELECT * FROM users;

Basic CQL queries for Cassandra.

Let’s Try →

Neo4j Cypher Basics

// Create nodes
CREATE (a:Person {name: "Alice"}), (b:Person {name: "Bob"});

// Create relationship
MATCH (a:Person {name: "Alice"}), (b:Person {name: "Bob"})
CREATE (a)-[:FRIEND]->(b);

// Query
MATCH (p:Person)-[:FRIEND]->(f)
RETURN p.name, f.name;

Basic graph queries using Cypher in Neo4j.

Let’s Try →

Elasticsearch DSL Queries

{
    "query": {
        "bool": {
        "must": [
        { "match": {title: "database" } },
        { "range": { "year": { "gte": 2020 } } }
        ]
        }
    }
}

JSON-based query DSL examples in Elasticsearch.

Let’s Try →

InfluxDB Time-Series Queries

-- Create measurement
INSERT temperature,location=room1 value=23.5

-- Select with time filter
SELECT value FROM temperature WHERE time > now() - 1h;

-- Aggregate
SELECT MEAN(value) FROM temperature WHERE time > now() - 24h GROUP BY time(1h);

InfluxQL examples for querying time-series data.

Let’s Try →

Frequently Asked Questions about Mql

What is Mql?

What are the primary use cases for Mql?

What are the strengths of Mql?

Flexible schema design. Powerful aggregation and filtering. High scalability for distributed systems. Wide ecosystem and language drivers. JSON-style document storage aligned with modern applications

What are the limitations of Mql?

How can I practice Mql typing speed?

CodeSpeedTest offers 10+ real Mql code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.