Performing Row and Column Counting : Count « Select Clause « SQL / MySQL

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SQL / MySQL » Select Clause » Count 
Performing Row and Column Counting

/*
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;

           
       
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2.Count and group
3.Use COUNT in select command
4.COUNT() and GROUP BY
5.Another Count and Group BY
6.Count and group by two columns
7.COUNT command with condition
8.COUNT with condition and group
9.Get GROUP BY for COUNT
10.Use COUNT with condition
11.Simple COUNT
12.Use COUNT and GROUP
13.Use COUNT, GROUP and HAVING
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