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Databases Explained for Beginners
A plain-language introduction to what databases are, how they store and protect information, and why almost every application depends on one.
Data and Technology
Databases and SQL
How data is stored, structured and queried.
Cleaning Messy Data Before Analysis
Learn the common problems in raw data, including duplicates, missing values, inconsistent formats and outliers, and a careful process for tidying them.
Data Warehouses and Data Lakes Compared
Compare data warehouses and data lakes: how each stores data for analysis, how schema-on-write differs from schema-on-read, and when organizations use both.
Database Indexes and Query Speed
See how a database index speeds up searches the way a book index does, what it costs in storage and write speed, and how to decide which columns to index.
Database Normalization Made Simple
A plain explanation of database normalization: why repeated data causes errors, and how the first three normal forms split tables to remove duplication.
Relational Databases and Tables in Plain Language
Learn how relational databases organize information into tables, rows and columns, and how primary and foreign keys connect one table to another.
Relational Versus NoSQL Databases
Compare relational tables with document, key-value, wide-column and graph stores, and learn the trade-offs that help decide which fits a project.
SQL Joins Explained With Everyday Examples
Understand INNER, LEFT, RIGHT and FULL joins using a simple customers and orders example, plus common mistakes such as duplicated rows and missing matches.
Your First SQL Queries
Learn the basics of SQL by selecting columns, filtering rows with WHERE, sorting with ORDER BY and limiting results, using a small example table.
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