SELECT `nazvanie` FROM `dischiplina` 
WHERE AVG(`ocenka`)>3 in 
     (SELECT `ocenka` FROM `uspev` WHERE `kod_disciplina`=`dischiplina`.`kod_dischiplina`)

SELECT fam FROM dannie 
WHERE kod_student IN
              (SELECT kod_student FROM uspev where ocenka='3') 

SELECT u.kod_student, d.fam 
FROM uspev u
      LEFT JOIN dannie d ON u.kod_student = d.kod_student
WHERE u.ocenka = 3 AND u.ocenka = 4

CREATE TABLE IF NOT EXISTS `uspev` (
  `ocenka` int(11) NOT NULL,

ocenka IN (3, 4)

AVG(Ocenka) > 3

SELECT fam FROM dannie 
WHERE kod_student IN
              (SELECT kod_student FROM uspev where (ocenka = 3) AND (ocenka = 4))

SELECT fam FROM dannie 
WHERE kod_student IN
              (SELECT kod_student FROM uspev where ocenka > AVG(ocenka))

SELECT kod_gruppy, COUNT(*) AS kolvo_studentov FROM dannie 
GROUP BY kod_gruppy

SELECT fam FROM dannie 
WHERE kod_student IN
              (SELECT kod_student FROM uspev where ocenka IN (3, 4))

SELECT fam FROM dannie 
WHERE kod_student IN
              (SELECT kod_student FROM uspev where ocenka > (SELECT AVG(ocenka) FROM uspev))