SQL MAX() function

Last update on April 04 2024 11:33:06 (UTC/GMT +8 hours)

MAX() function

The aggregate function SQL MAX() is used to find the maximum value or highest value of a certain column or expression. This function is useful to determine the largest of all selected values of a column.

Syntax:

MAX ([ALL | DISTINCT] expression )

DB2 and Oracle Syntax:

MAX ([ALL | DISTINCT] expression ) OVER (window_clause)

Parameters:

Name	Description
ALL	Applies to all values.
DISTINCT	Consider each unique value. DISTINCT is not meaningful with MAX function.
expression	Expression made up of a single constant, variable, scalar function, or column name or any combination of arithmetic, bitwise, and string operators. MAX can be used with numeric, character, and datetime columns, but not with bit columns. Aggregate functions and subqueries are not permitted.

DBMS Support: COUNT() function

DBMS	Command
MySQL	Supported
PostgreSQL	Supported
SQL Server	Supported
Oracle	Supported

Syntax diagram - MAX() function

Example:

To get maximum 'ord_amout' from the 'orders' table, the following SQL statement can be used :

Sample table: orders


SELECT MAX(ord_amount)  -- Selects the maximum value of the 'ord_amount' column
FROM orders;  -- Specifies the 'orders' table as the source of data

Explanation:

SELECT MAX(ord_amount): This is the main part of the SQL query. It uses the MAX() function to calculate the maximum value of the 'ord_amount' column in the 'orders' table. The result will be a single value representing the maximum value found in the 'ord_amount' column.

FROM orders: This specifies the source of the data for the query, which is the 'orders' table. The FROM keyword is used to indicate the table from which the data will be selected. In this case, it selects data from the 'orders' table.

Relational Algebra Expression:

Relational Algebra Tree:

Output:

MAX(ORD_AMOUNT)
---------------
           4500

Pictorial Presentation:

SQL MAX() with addition of two columns

To get the maximum value of (opening_amt+receive_amt) from the customer table, the following SQL statement can be used :

Sample table: customer


SELECT MAX(opening_amt + receive_amt)  -- Selects the maximum value of the sum of 'opening_amt' and 'receive_amt'
FROM customer;  -- Specifies the 'customer' table as the source of data

Explanation:

SELECT MAX(opening_amt + receive_amt): This is the main part of the SQL query. It calculates the sum of the 'opening_amt' and 'receive_amt' columns for each row in the 'customer' table and then selects the maximum value among these sums. The MAX() function is used to find the maximum value.

FROM customer: This specifies the source of the data for the query, which is the 'customer' table. The FROM keyword is used to indicate the table from which the data will be selected. In this case, it selects data from the 'customer' table.

Relational Algebra Expression:

Relational Algebra Tree:

Output:

MAX(OPENING_AMT+RECEIVE_AMT)
----------------------------
                       19000

Note: Outputs of the said SQL statement shown here is taken by using Oracle Database 10g Express Edition

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