lesson 05 Filtering & sorting · beginner

Combine conditions

Combine filters with AND, OR and parentheses.

the idea

AND requires every condition; OR requires at least one. AND is evaluated before OR, so mixed conditions need parentheses to say what you mean. NOT reverses a condition.

Dataset: Retail

The tables the challenges use, with their first 6 rows. Under each column name: the kind of value it holds, and which table it links to.

worked example

Run these steps in order to see the idea before you write your own query. The step marked “the pattern” is what the challenges ask for. Running the example does not count toward progress.

1. 1

   Require two conditions at once. Run this. AND means both country and order_type must match—here, Spanish cancellations only.the pattern

   example.sql Run

   sql›

   SELECT order_id, country, order_type
   FROM orders
   WHERE country = 'Spain' AND order_type = 'cancellation';

2. 2

   Use parentheses with OR. Run this. Parentheses group the OR so you keep sale orders from Spain or Portugal.

   step-2.sql Run

   sql›

   SELECT order_id, country, order_type
   FROM orders
   WHERE order_type = 'sale'
     AND (country = 'Spain' OR country = 'Portugal');

common mistake

order_type = 'sale' AND country = 'Germany' OR country = 'France' also returns French cancellations, because AND binds first.