distinct

DISTINCT takrorlangan qatorlarni olib tashlaydi.

SELECT DISTINCT city FROM students;                 -- har shahar bir marta
SELECT DISTINCT city, faculty FROM students;        -- juftliklar bo‘yicha takrorsiz
SELECT COUNT(DISTINCT city) FROM students;          -- nechta turli shahar

DISTINCT butun qatorga ta’sir qiladi, bitta ustunga emas: SELECT DISTINCT a, b — (a, b) juftliklari takrorsiz.