DISTINCT: (SELECT DISTINCT city FROM customers.
ORDER BY: used at the end of query.
AND: All of the tests must be true.
OR: Only one of them need to be true.
- Q: We want all customer' city, name and id number whose id is 1 or 2 and live in Istanbul?
IN: Instead of using 3 OR statements we can use IN keywords.
SELECT * FROM customer_all WHERE id IN (3, 5, 127, 1346) ORDER BY id
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