5.1 SQL
Every entry filed under SQL and its subtopics.
What kind of help
What do these mean?
- Beginner
- You are new to this topic.
- Intermediate
- You use it, and want to get better.
- Advanced
- You know it well and need the details.
- Guided project
- Build something small from start to finish, step by step.
- Explains an idea
- Plain words on how something works and why.
- Step by step
- Numbered steps to get one task done.
- Cheat sheet
- Commands and options in a table, to look up fast.
- Fixes an error
- An error message, what it means, and how to solve it.
5 entries match these filters
- 0293 What is SQL? SQL is the language you use to ask a relational database questions and to add, change or delete its data. Beginner · Explains an idea · Any system Article Queries 15 Oct 2026
- 0295 What is a transaction? A transaction groups several database changes so they all happen together or not at all, keeping the data consistent. Beginner · Explains an idea · Any system Article Queries 15 Oct 2026
- 0296 What is a primary key? A primary key is the column that uniquely identifies each row in a table, like an ID number nobody else can have. Beginner · Explains an idea · Any system Article Queries 15 Oct 2026
- 0297 What is a foreign key? A foreign key is a column that points to the primary key of another table, linking related rows together. Beginner · Explains an idea · Any system Article Joins 15 Oct 2026
- 0294 What is an index (database)? A database index is a lookup structure that lets the database find rows fast instead of reading the whole table. Beginner · Explains an idea · Any system Article Indexes & performance 15 Oct 2026