SQL - MAX Function

SQL MAX function is used to find out the record with maximum value among a record set.

To understand MAX function consider an employee_tbl table which is having following records:

SQL> SELECT * FROM employee_tbl;
+------+------+------------+--------------------+
| id   | name | work_date  | daily_typing_pages |
+------+------+------------+--------------------+
|    1 | John | 2007-01-24 |                250 |
|    2 | Ram  | 2007-05-27 |                220 |
|    3 | Jack | 2007-05-06 |                170 |
|    3 | Jack | 2007-04-06 |                100 |
|    4 | Jill | 2007-04-06 |                220 |
|    5 | Zara | 2007-06-06 |                300 |
|    5 | Zara | 2007-02-06 |                350 |
+------+------+------------+--------------------+
7 rows in set (0.00 sec)

Now suppose based on the above table you want to fetch maximum value of daily_typing_pages, then you can do so simply using the following command:

SQL> SELECT MAX(daily_typing_pages)
    -> FROM employee_tbl;
+-------------------------+
| MAX(daily_typing_pages) |
+-------------------------+
|                     350 |
+-------------------------+
1 row in set (0.00 sec)

You can find all the records with maxmimum value for each name using GROUP BY clause as follows:

SQL> SELECT id, name, work_date, MAX(daily_typing_pages)
    -> FROM employee_tbl GROUP BY name;
+------+------+------------+-------------------------+
| id   | name | work_date  | MAX(daily_typing_pages) |
+------+------+------------+-------------------------+
|    3 | Jack | 2007-05-06 |                     170 |
|    4 | Jill | 2007-04-06 |                     220 |
|    1 | John | 2007-01-24 |                     250 |
|    2 | Ram  | 2007-05-27 |                     220 |
|    5 | Zara | 2007-06-06 |                     350 |
+------+------+------------+-------------------------+
5 rows in set (0.00 sec)

You can use MIN Function alongwith MAX function to find out minimum value as well. Try out following example:

SQL> SELECT MIN(daily_typing_pages) least, MAX(daily_typing_pages) max
    -> FROM employee_tbl;
+-------+------+
| least | max  |
+-------+------+
|   100 |  350 |
+-------+------+
1 row in set (0.01 sec)