SELECT

Choose the columns you need.

SELECT user_id, country, created_at
FROM users;

SELECT user_id, country, created_at
FROM users;

WHERE

Filter rows.

SELECT user_id, country
FROM users
WHERE country = 'IN';

SELECT user_id, country
FROM users
WHERE country = 'IN';

Common operators

• ==, !=!=, >>, <<, >=>=, <=<=
• IN (...)IN (...)
• BETWEEN a AND bBETWEEN a AND b
• LIKE '%text%'LIKE '%text%'
• IS NULLIS NULL / IS NOT NULLIS NOT NULL

SELECT user_id, created_at, plan
FROM users
WHERE country IN ('IN', 'US')
  AND plan != 'free'
  AND created_at >= '2025-01-01';

SELECT user_id, created_at, plan
FROM users
WHERE country IN ('IN', 'US')
  AND plan != 'free'
  AND created_at >= '2025-01-01';

ORDER BY

SELECT user_id, created_at
FROM users
ORDER BY created_at DESC
LIMIT 20;

SELECT user_id, created_at
FROM users
ORDER BY created_at DESC
LIMIT 20;

LIMIT

Limits are great for exploration.

SELECT *
FROM orders
LIMIT 50;

SELECT *
FROM orders
LIMIT 50;

The order SQL actually runs in

This trips up almost every beginner: SQL is not executed top-to-bottom in the order you type it. The database picks the table first, filters rows, then figures out which columns to show, and sorts/limits last.

  flowchart TD
  A["FROM users"] --> B["WHERE country = 'IN'"]
  B --> C["SELECT user_id, country"]
  C --> D["ORDER BY created_at DESC"]
  D --> E["LIMIT 20"]

That’s why you can filter on a column in WHEREWHERE that you never mention in SELECTSELECT — the engine already resolved WHEREWHERE against the full table before it trimmed the column list.

🧪 Try It Yourself

Exercise 1 – SELECT specific columns

Exercise 2 – WHERE with multiple conditions

Exercise 3 – ORDER BY and LIMIT together

Next

Once you’re comfortable filtering and sorting single tables, move on to Aggregations (COUNT, SUM, AVG) and GROUP BY to start computing metrics instead of just listing rows.