SQL MAX command: MySQL on Maximum or highest value in a field

SQL MAX Command

Some time we will be searching for the maximum value in a field of any MySql table. MAX sql command will return the record with maximum or highest value in the SQL table. Same way we can get the minimum value of a range of records by using SQL MIN command

What happen if we apply MAX command to a non numeric field? We will get the record with highest alphabet. But the best way to use MAX command is to apply it in a numeric field.

id	name	class	mark
1	John Deo	Four	75
2	Max Ruin	Three	85
3	Arnold	Three	55
4	Krish Star	Four	60
5	John Mike	Four	60
6	Alex John	Four	55

We will apply the MAX command here like this to the field mark

SELECT max( mark ) FROM `student`

Related Tutorial Descending Order Top 3 records MySQL Min

max(mark)

The command collected the maximum value of the mark field and displayed. We can define some header like this also.


SELECT MAX(mark) as max_mark FROM `student`

max_mark
85

Using Subqueries

To display all fields like name, class, id along with the highest mark we can use like this. This will display one record with all details of the highest mark

SELECT id,name,class,MAX(mark) as max_mark FROM `student`

This will give wrong result.

As you can see below the above query will display Maximum mark but not the matching id, name, class. So we will try by using sub-query

id	name	class	max_mark
2	Max Ruin	Three	85

We can get matching output of id, name,class by using where clause by matching with maximum mark using subquery

SELECT * FROM `student` WHERE mark=(select max(mark) from student)

id	name	class	mark	sex
33	Kenn Rein	Six	96	female

Maximum mark in each class by using Group By

Now let us find out what is the maximum mark ( or highest ) in each class. Here we can use the Group By command to find out the maximum mark obtained by each class

SELECT class, max( mark ) as max_mark FROM
`student` GROUP BY class

class	max_mark
Four	75
Three	85

You can see above that maximum mark of each class is displayed. Since we have two class in our table so the sql command has returned two class with highest mark in each of them. We have to use Group By clause if we ask for the query to return any other field name other than the max. Otherwise system will generate error.

We can add condition to the sql command to get our desired result. We can add one Where clause to the query to consider records for a perticular class only ( say Four)


SELECT max( mark ) as maximu_mark, class FROM student where class ='Four' GROUP BY class

max_mark	class
75	Four

When integer is stored in VARCHAR field

If numbers are stored in VARCHAR field then MAX command will return based on the first digit. Example.

SELECT MAX ( t1) from max_value

We stored these number in t1 ( VARCHAR ) column , 1,2,3,4,5,6,12,13

The output will be 6 ( Why not 13 ? )

We need to convert the data to integer first by using CONVERT function. Here is the correct query

SELECT MAX(CONVERT(t1,UNSIGNED))  FROM `max_value`

The output will be 13 .

To test the result here is the SQL dump of our max_value table.

CREATE TABLE IF NOT EXISTS `max_value` (
  `t1` varchar(2) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

--
INSERT INTO `max_value` (`t1`) VALUES
('1'),
('2'),
('3'),
('4'),
('5'),
('6'),
('12'),
('13');

Getting Max from a date field

We can get Maximum value from a date field like this.

SELECT MAX(exam_dt) FROM student_mark

There are two exam dates available for each month. We may require the 2nd exam date for each month.

SELECT MAX(exam_dt) from student_mark group by month(exam_dt)

You can get SQL Dump of student_mark table here

Storing record with Maximum mark in new table

CREATE TABLE student_max SELECT * FROM `student` WHERE mark=(select max(mark) from student)

The new table student_max will retain the same table structure as student
If the table is already available, then use insert command.

INSERT INTO student_max SELECT * FROM `student` WHERE mark=(select max(mark) from student)

Using MAX Query in PHP Script

We can use above queries by using PHP Script. First we will connect to MySQL database.

Here is the sample code.

<?Php
require "config.php";

$count="SELECT class, max( mark ) as max_mark FROM `student` GROUP BY class";

echo "<table>";
echo "<tr><th>class</th><th>max_mark</th></tr>";
foreach ($dbo->query($count) as $row) {
echo "<tr ><td>$row[class]</td><td>$row[max_mark]</td></tr>";
}
echo "</table>";
?>

▼ More on Math functions in SQL