Data and Databases
What Is a Database?
A database stores organized data so it can be searched, changed and protected. Learn what one is, how it differs from a file, and where you already use one.
- Beginner
- Concept
- 6 min read
Updated October 30, 2026
Data and Databases
Storing, finding and trusting data.
Nearly every app, website and report depends on stored data. Knowing how that data is organized tells you why some questions are easy to answer and others are slow, and why one wrong value can spread through a whole system.
These entries begin with what a database is and how it differs from a spreadsheet, then explain tables and keys, the basics of SQL, joins and the main kinds of databases. They end with two practical skills: cleaning messy data and designing a simple database.
Who it helps: Start here if you work with spreadsheets and want to go further, or if you are curious how apps remember things.
Entries in this area (9)
Data and Databases
Spreadsheet vs Database: When to Use Which
Compare spreadsheets and databases on rules, shared editing, linked data and size. Use a short checklist to decide which tool fits your project.
- Beginner
- Concept
- 6 min read
Updated October 30, 2026
Data and Databases
Tables, Rows, Columns and Primary Keys
Learn what tables, rows and columns are, why every table needs a primary key, and how a foreign key links one table to another, with a class list.
- Beginner
- Concept
- 7 min read
Updated October 30, 2026
Data and Databases
SQL Basics: Reading Data with SELECT
Learn to read data with SQL: pick columns with SELECT, filter rows with WHERE, sort with ORDER BY and cap results with LIMIT, using a bike shop table.
- Beginner
- Skill
- 5 min read
Updated October 30, 2026
Data and Databases
SQL Joins Explained with Simple Examples
Learn what a SQL join does, how INNER, LEFT, RIGHT and FULL joins differ, and how to avoid the common mistakes, using two small tables.
- Intermediate
- Concept
- 5 min read
Updated October 30, 2026
Data and Databases
Relational vs NoSQL Databases
Compare relational and NoSQL databases: how each stores data, where each fits, and how to choose, shown with the same recipe box stored both ways.
- Intermediate
- Concept
- 6 min read
Updated October 30, 2026
Data and Databases
CSV vs JSON: Common Data File Formats
Compare CSV and JSON: how each file is written, what each handles well, where each breaks, and which to pick, shown with one food truck menu.
- Beginner
- Concept
- 6 min read
Updated October 30, 2026
Data and Databases
Data Cleaning Basics: Fixing Messy Data
Learn a repeatable way to clean messy data: inspect, copy, fix spacing, case, dates, blanks and duplicates, then check the result. Includes SQL examples.
- Intermediate
- Skill
- 6 min read
Updated October 30, 2026
Data and Databases
Database Design Basics: Entities and Relationships
Learn how to design a small database: list entities, choose keys, map one-to-many and many-to-many relationships, and avoid repeated data, with a music school.
- Intermediate
- Skill
- 6 min read
Updated October 30, 2026