Give the average.
SELECT AVG(grade)
FROM grades;
SELECT COUNT(*) FROM student;
SELECT COUNT(DISTINCT(car_model)) from car;
used with distinct, it will not count duplicate.
String function that convert character to lower/upper case
SELECT UPPER(name) FROM student;
SELECT LOWER(name) FROM student;
Return the min/max value from a column. Also work with string (return based on the number of character).
SELECT MAX(grade) FROM grade;