Database

Learn the first three normal forms, why reducing duplication matters, and the trade-offs of using denormalization to reduce JOINs and improve read performance.

Learn how ORM addresses the mismatch between object-oriented programming and relational databases. Explore JPA, ORM trade-offs, the N+1 problem, and how Fetch Join can solve it.

Learn to optimize slow SQL queries by analyzing execution plans, using indexes correctly, and reducing unnecessary data processing.

Learn how database transactions protect data integrity and how the ACID properties ensure atomicity, consistency, isolation, and durability.

Compare RDBMS and NoSQL by data models, schemas, scalability, and transactions, then learn when each database is the right fit.

Learn how database indexes improve SELECT performance, why indexing everything is impractical, and how faster reads trade off against slower writes.

Learn advanced MongoDB features with Python and PyMongo: transactions, GridFS for large files, Change Streams, practical development tips, and an introduction to the asynchronous Motor driver.

Learn advanced PyMongo queries, index management, and the foundations of MongoDB’s Aggregation Framework through practical examples.

Learn PyMongo fundamentals, connect to MongoDB Atlas, perform CRUD operations, and work with BSON types in Python.

Learn to connect Python and Java applications to MongoDB Atlas using PyMongo and the MongoDB Java Driver, with basic connection examples.

Connect a Node.js application to MongoDB Atlas with the official driver and perform basic CRUD operations.

Learn to use MongoDB Compass and the mongodump, mongorestore, mongoimport, and mongoexport utilities for visual database management, backups, restores, and data exchange.

An introduction to Atlas, MongoDB’s cloud database service. Learn its benefits and features, then follow a practical guide to creating an account, launching a free cluster, and connecting an application.

Learn to secure MongoDB with authentication, role-based authorization, and encryption for data at rest and in transit.

Learn how to configure a MongoDB sharded cluster for large datasets, including concepts, components, shard keys, setup steps, and management commands.

Learn to configure a local MongoDB replica set, verify replication, test automatic failover, and understand arbiters and read preferences.

Learn how to speed up MongoDB queries and improve overall performance. Explore why indexes matter, their types, how to create and manage them, and query analysis and optimization with explain.

Learn to query MongoDB with comparison and logical operators, and use the Aggregation Framework to filter, group, transform, and analyze data.

Learn MongoDB CRUD operations—create, read, update, and delete—through hands-on MongoDB Shell examples.

Learn how MongoDB stores documents and BSON, and when to model relationships by embedding related data or referencing separate documents.

Install MongoDB Community Server on Windows, macOS, or Linux, then verify the service and review basic configuration.

Learn how MongoDB stores documents and organizes collections, and how replica sets and sharding provide availability and scalability.

Learn what MongoDB is, how document-oriented databases work, how MongoDB originated, and how it compares with relational databases.

Explore MySQL and Oracle regular expressions, CUBE and GROUPING SETS, advanced window frames, and pivoting and unpivoting.

A practical guide to CTEs, recursive queries, subqueries, ROLLUP, and string aggregation in MySQL and Oracle, with SQL examples and notes.

A practical guide to advanced SQL for coding tests, covering string functions, JOINs, UNION, window functions, and date/time functions in MySQL and Oracle.

Solve the Programmers SQL exercise by comparing each E. coli colony's size with the maximum for its year.

A practical reference to SELECT, filtering, joins, aggregation, subqueries, and other SQL query syntax used in coding tests.