Mega Code Archive
Eliminating Duplicate Data Using DISTINCT 2
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/*
mysql> SELECT DISTINCT Mark, ExamID FROM Exam;
+------+--------+
| Mark | ExamID |
+------+--------+
| 55 | 1 |
| 73 | 2 |
| 44 | 3 |
| 55 | 4 |
| 73 | 5 |
| 44 | 6 |
+------+--------+
6 rows in set (0.00 sec)
*/
/* Prepare the data */
Drop TABLE Exam;
CREATE TABLE Exam (
StudentID INT NOT NULL,
ExamID INT NOT NULL,
Mark INT,
IfPassed SMALLINT
)TYPE = InnoDB;
/* Insert data for testing */
INSERT INTO Exam (StudentID,ExamID,Mark,IfPassed) VALUES (1,1,55,1);
INSERT INTO Exam (StudentID,ExamID,Mark,IfPassed) VALUES (1,2,73,0);
INSERT INTO Exam (StudentID,ExamID,Mark,IfPassed) VALUES (2,3,44,1);
INSERT INTO Exam (StudentID,ExamID,Mark,IfPassed) VALUES (1,4,55,1);
INSERT INTO Exam (StudentID,ExamID,Mark,IfPassed) VALUES (1,5,73,0);
INSERT INTO Exam (StudentID,ExamID,Mark,IfPassed) VALUES (2,6,44,1);
/* Real command */
SELECT DISTINCT Mark, ExamID FROM Exam;
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