PostgreSQL - MAX Function

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

To understand the MAX function, consider the table COMPANY having records as follows −

testdb# select * from COMPANY;
 id | name  | age | address   | salary
----+-------+-----+-----------+--------
  1 | Paul  |  32 | California|  20000
  2 | Allen |  25 | Texas     |  15000
  3 | Teddy |  23 | Norway    |  20000
  4 | Mark  |  25 | Rich-Mond |  65000
  5 | David |  27 | Texas     |  85000
  6 | Kim   |  22 | South-Hall|  45000
  7 | James |  24 | Houston   |  10000
(7 rows)

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

testdb=# SELECT MAX(salary) FROM COMPANY;

The above given PostgreSQL statement will produce the following result −

  max
-------
 85000
(1 row)

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

testdb=# SELECT id, name, MAX(salary) FROM COMPANY GROUP BY id, name;

The above given PostgreSQL statement will produce the following result −

 id | name  |  max
----+-------+-------
  4 | Mark  | 65000
  7 | James | 10000
  6 | Kim   | 45000
  3 | Teddy | 20000
  2 | Allen | 15000
  5 | David | 85000
  1 | Paul  | 20000

You can use the MIN Function along with the MAX function to find out minimum value as well. Try out the following example −

testdb=# SELECT MIN(salary), MAX(salary) max FROM company;

The above given PostgreSQL statement will produce the following result −

  min  |  max
-------+-------
 10000 | 85000
(1 row)