SQL Basics

What is SQL Basics?

Within Computer Science, which covers algorithms, programming, data, networks, hardware and safe, responsible use of technology, this topic explains SQL Basics. Computing topics explain how software, hardware and data work, with diagrams and models that show each step in order.

Check that you can explain SQL Basics in your own words and give one example from everyday life. If you can do that, you have understood the core idea.

Understanding SQL Basics helps you design, test and explain programs, websites and systems, from small projects to exam questions.

SQL Basics in detail

SQL (Structured Query Language) is the standard language for working with relational databases. SELECT retrieves data: SELECT name, age FROM students WHERE age > 15 ORDER BY name. The WHERE clause filters rows, ORDER BY sorts, and * selects all columns.

Other commands include INSERT INTO to add records, UPDATE to change data and DELETE to remove records, CREATE TABLE to define a table, and JOIN to combine data from related tables. Functions such as COUNT, SUM and AVG summarise data. SQL injection is a security threat that uses malicious input, so inputs should be validated.

How the interactive helps you understand SQL Basics

Click a step, or use the Previous and Next buttons, to move through the sequence one stage at a time. Auto-play moves on for you.

Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of SQL Basics.

Real-life uses and examples

• Apply SQL Basics when you design a small program, website or spreadsheet.
• Explain SQL Basics to someone new to computing by comparing it to a familiar process.
• Trace through a process that uses SQL Basics to check what it does step by step.

Common mistakes to avoid

• Testing only the normal case and forgetting the edge cases.
• Using the term without being able to say what the computer actually does.
• Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.