/*
mysql> SELECT COUNT(*) AS NumberOfExams,
-> COUNT(DISTINCT SustainedOn) AS UniqueDates,
-> COUNT(Comments) AS ExamsWithComments
-> FROM Exam;
+---------------+-------------+-------------------+
| NumberOfExams | UniqueDates | ExamsWithComments |
+---------------+-------------+-------------------+
| 3 | 3 | 3 |
+---------------+-------------+-------------------+
1 row in set (0.00 sec)
*/
/* Create the table */
Drop TABLE Exam;
CREATE TABLE Exam (
ExamID INT NOT NULL PRIMARY KEY,
SustainedOn DATE,
Comments VARCHAR(255)
)TYPE = InnoDB;
/* Insert data */
INSERT INTO Exam (ExamID,SustainedOn,Comments) VALUES (1,'2003-03-12','Java test');
INSERT INTO Exam (ExamID,SustainedOn,Comments) VALUES (2,'2003-03-13','C# test');
INSERT INTO Exam (ExamID,SustainedOn,Comments) VALUES (3,'2003-03-11','JavaScript test');
/* Real command */
SELECT COUNT(*) AS NumberOfExams,
COUNT(DISTINCT SustainedOn) AS UniqueDates,
COUNT(Comments) AS ExamsWithComments
FROM Exam;