SQL , . , , , , , , . .
:
UNION ; , ;
UNION ALL ; , ;
INTERSECT ; , ;
MINUS .
:
-- ( ),
SELECT N_z FROM Students
MINUS
SELECT N_z FROM St_Hobby;
, , (, ). , MAX, , , , ..
ORACLE , , . ( ) 1 . WHERE. SELECT , , 5, 50 500 .
, , :
SELECT __1 [, __2 ]
FROM _
WHERE (ROWNUM >= _)
AND (ROWNUM <= _)
ORDER BY _;
, , . , ( ) , :
SELECT N_z, COUNT(N_z)
FROM Students
WHERE ROWNUM<=2
GROUP BY N_z
ORDER BY COUNT(N_z)DESC;