Lesson 02 / 9·7 minFree

SELECT and FROM: Asking Questions

The foundation of every SQL query — what you want and where to find it

SQL is a question-answering language. Every query is a question you ask the database. SELECT defines what you want to know. FROM defines where to look. That's 80% of SQL right there.

Your first query

The simplest possible SQL queries

-- Get everything from the users table (* means "all columns")
SELECT * FROM users;

-- Get only specific columns
SELECT name, email FROM users;

-- Get just the name column
SELECT name FROM users;

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SELECT is the question. FROM is the filing drawer.

You walk to the filing cabinet and pull open the "customers" drawer (FROM customers). Then you say: I want to see the name and email from each file, not all the other details (SELECT name, email). SQL reads exactly like this natural language question — just with a strict word order.

Reading query results

Every SELECT query returns a result set — a temporary table with the data you asked for. Nothing is changed. SELECT never modifies data. It only reads.

SELECT name, plan FROM users — result:

name    | plan
--------+------
Sarah   | pro
Alex    | free
Priya   | pro

SQL is case-insensitive for keywords

SELECT, select, Select — all the same. By convention, keywords are UPPERCASE and column/table names are lowercase. This makes queries easier to read at a glance. Always end a query with a semicolon (;) — it tells the database the query is complete.

Useful SELECT tricks

More SELECT patterns

-- Rename a column in the result (alias)
SELECT name AS customer_name, email AS contact FROM users;

-- Arithmetic in SELECT
SELECT name, price, price * 1.2 AS price_with_vat FROM products;

-- Combine text columns
SELECT first_name || ' ' || last_name AS full_name FROM users;

-- Count how many rows (returns one number)
SELECT COUNT(*) FROM users;

▶ Build your first query step by step

Start with SELECT *

SELECT * FROM users;

Result

Returns all columns and all rows — every piece of data in the table.

Pick specific columns

SELECT id, name, email FROM users;

Result

Returns only those 3 columns for every row.

Count the rows

SELECT COUNT(*) FROM users;

Result

3 (or however many users you have)

Add an alias

SELECT COUNT(*) AS total_users FROM users;

Result

Same result but column is labelled "total_users" in the output.

→

Try this

Write a query to get the name and plan of every user in your database. Then modify it to also include the created_at column. Then write a query that just counts how many users you have.

What Is a Database?WHERE: Filtering Your Results