/* Write your PL/SQL query statement below */


-- create a table
CREATE TABLE Courses (
    student VARCHAR2, 
    class VARCHAR2,
    CONSTRAINT PK_STUDENT PRIMARY KEY (student, class)
);
-- insert some values
INSERT INTO Courses (class, student) VALUES ('Math', "A");
INSERT INTO Courses (class, student) VALUES ('ENGLISH', "B");
INSERT INTO Courses (class, student) VALUES ('Math', "C");
INSERT INTO Courses (class, student) VALUES ('BIOLOGY', "D");
INSERT INTO Courses (class, student) VALUES ('Math', "E");
INSERT INTO Courses (class, student) VALUES ('Math', "F");
INSERT INTO Courses (class, student) VALUES ('COMPUTER', "G");
INSERT INTO Courses (class, student) VALUES ('Math', "H");
INSERT INTO Courses (class, student) VALUES ('Math', "I");


-- fetch some values
-- SELECT class FROM Courses WHERE COUNT(CLASS) > 1;
SELECT (CLASS) FROM COURSES GROUP BY CLASS HAVING COUNT((STUDENT)) >=5;
-- no change with using DISTINCT
-- SELECT (CLASS) FROM COURSES GROUP BY CLASS HAVING COUNT(DISTINCT(STUDENT)) >=5;