Understand SQL's basic architecture and how queries are executed under the hood.
SQL—short for Structured Query Language—is the standard language used to interact with relational databases. It's powerful, widely adopted, and surprisingly approachable for beginners.
But how does SQL actually work under the hood? What happens when you run a query? In this guide, we’ll walk through how SQL translates your human-readable commands into precise database operations.
Want to see it all in action? Try your own queries in the Galaxy SQL Editor.
SQL is a declarative language, which means you describe what you want from the database (e.g., “get all users with verified emails”), and the database decides how to do it.
Unlike imperative languages like Python or JavaScript, you don’t tell SQL how to fetch data step by step. You just write a query, and the query engine handles the rest.
Here’s what happens behind the scenes when you run a query like:
SELECT name FROM users WHERE is_verified = true;
The database parses your SQL query to check for syntax errors and validate structure.
The database generates a query plan—an internal blueprint that determines the most efficient way to access the requested data. This might include:
You can inspect these plans using EXPLAIN—try it out in Galaxy’s SQL Editor.
The database accesses disk, memory, or cache to fetch the necessary data. It applies filters (WHERE), projections (SELECT), ordering (ORDER BY), and any aggregations (COUNT, SUM, etc).
Once processed, the result is returned to the client—your app, dashboard, or terminal.
SQL is divided into a few main categories:
Used to retrieve data:
SELECTFROMWHEREGROUP BY, ORDER BY, LIMITExample:
SELECT name FROM users WHERE country = 'Canada';
Learn how to write your first query in our SQL query starter guide.
Used to define and modify database structure:
CREATE, ALTER, DROP, RENAMEExample:
CREATE TABLE users (
id SERIAL PRIMARY KEY,
email VARCHAR(255),
created_at TIMESTAMP
);
See how types work in our SQL Data Types guide.
Used to change the data:
INSERT, UPDATE, DELETEExample:
INSERT INTO users (email) VALUES ('jane@example.com');
Learn more in our INSERT/UPDATE/DELETE guide.
Used to manage access:
GRANT, REVOKE (not covered in detail in this beginner series)SQL may look simple, but it’s surprisingly expressive:
SQL is a standard, but every database has its own flavor. Most commands are the same, but differences exist in:
SERIAL, AUTO_INCREMENT, TEXT, BOOLEAN)NOW() vs CURRENT_TIMESTAMP)LIMIT vs TOP, ILIKE for case-insensitive match)Galaxy supports multiple dialects, and you can toggle between them in the SQL Editor.
SQL has been around since the 1970s—and it’s more popular than ever. From startups to Fortune 500 companies, SQL remains the universal language for:
SQL might look deceptively simple, but behind every query is a powerful system parsing, planning, optimizing, and executing. The better you understand that system, the more efficient and effective your queries will be.
Whether you’re writing simple filters or optimizing for big data workloads, SQL is a tool every developer and analyst should master.
Ready to start writing your own? Head over to the Galaxy SQL Editor and run your first real query.
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