SQL vs NoSQL: what's the difference?SQL vs NoSQL compared: how relational and non-relational databases store data, the ACID and BASE trade-offs, and how to choose between them.What is a database index? How database indexes work and when to use themA database index is a data structure that lets a database find rows without scanning the whole table, usually a balanced tree (B-tree) ordered by the indexed columns. It makes equality, range, sort and join queries fast, at the cost of write overhead and storage. This guide explains how indexes work, clustered vs non-clustered, and when (and when not) to create one.What is database normalization? 1NF, 2NF, 3NF, and BCNF explainedDatabase normalization is the process of structuring a relational database according to a series of normal forms to reduce data redundancy and improve data integrity. This guide explains why normalization matters, walks through 1NF, 2NF, 3NF, BCNF, 4NF, and 5NF with worked examples, and when denormalization is the right trade-off.What is a relational database? How relational databases workA relational database stores data in tables of rows and columns connected by keys, using SQL to query and manage it. This guide covers the relational model, normalization, transactions, and when to choose an RDBMS.What is a SQL query? How SELECT, JOIN and aggregation workA SQL query is a declarative statement that asks a relational database for data. This guide explains the SELECT statement, WHERE filtering, JOIN across tables, GROUP BY aggregation, and how to read a query plan. 