Grouping Data: 03 Using the HAVING Clause 1 : Group « Select Clause « SQL / MySQL






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Grouping Data: 03 Using the HAVING Clause 1

   
/*

mysql> Select * from StudentExam;
+-----------+------+------------+
| StudentID | Mark | Comments   |
+-----------+------+------------+
|        10 |   76 | Java       |
|        10 |   65 | C#         |
|        10 |   79 | JavaScript |
|        11 |   66 | Java       |
|        11 |   85 | C#         |
|        11 |   69 | JavaScript |
+-----------+------+------------+
6 rows in set (0.00 sec)

mysql> /* Real command */
mysql> SELECT StudentID, AVG(Mark) AS AverageMark
    -> FROM StudentExam
    -> GROUP BY StudentID
    -> HAVING AVG(Mark) < 50 OR AVG(Mark) > 70;
+-----------+-------------+
| StudentID | AverageMark |
+-----------+-------------+
|        10 |     73.3333 |
|        11 |     73.3333 |
+-----------+-------------+
2 rows in set (0.01 sec)


*/

/* Create table */
Drop TABLE StudentExam;

CREATE TABLE StudentExam (
   StudentID  INT NOT NULL,
   Mark       INT,
   Comments   VARCHAR(255)
   
)TYPE = InnoDB;

/* Insert data */
INSERT INTO StudentExam (StudentID,Mark,Comments) VALUES (10,76,'Java');
INSERT INTO StudentExam (StudentID,Mark,Comments) VALUES (10,65,'C#');
INSERT INTO StudentExam (StudentID,Mark,Comments) VALUES (10,79,'JavaScript');

INSERT INTO StudentExam (StudentID,Mark,Comments) VALUES (11,66,'Java');
INSERT INTO StudentExam (StudentID,Mark,Comments) VALUES (11,85,'C#');
INSERT INTO StudentExam (StudentID,Mark,Comments) VALUES (11,69,'JavaScript');

Select * from StudentExam;

/* Real command */
  
SELECT StudentID, AVG(Mark) AS AverageMark
FROM StudentExam
GROUP BY StudentID
HAVING AVG(Mark) < 50 OR AVG(Mark) > 70;








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