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PostgreSQL - MAX() Function - GeeksforGeeks

Last Updated : 15 Jul, 2025

The MAX() function in PostgreSQL is a versatile and powerful aggregate function used to determine the maximum value within a set of values. It plays a crucial role in data analysis, reporting, and SQL query optimization. This function can be applied in SELECT, WHERE, GROUP BY, and HAVING clauses, making it indispensable for analyzing data efficiently.

In this article, we will explain the PostgreSQL MAX() function, understand its syntax, explore examples with outputs, and highlight its important features to help us understand its full potential.

The MAX() function in PostgreSQL retrieves the highest value from a specified column or expression. It works with numeric, date, or text data types and ignores NULL values in computations. This function is often paired with GROUP BY, HAVING, or WHERE clauses for more complex queries.

Syntax

MAX(expression)

expression: The column or calculated expression from which we want to find the maximum value.

Let us take a look at some practical examples of the MAX() function in PostgreSQL to better understand its functionality and use cases. These examples will demonstrate how the function can be applied to different scenarios, such as finding the highest value in a column, grouping results, and applying conditions to our queries for more refined results.

The following query retrieves the highest payment amount recorded in the payment table. It ensures that only the largest value is retrieved, ignoring any NULL entries.

Query:

SELECT MAX(amount)
FROM payment;

Output

Explanation:

This query scans the 'amount' column in the 'payment' table and returns the maximum value, which represents the highest payment made by any customer.

The next example demonstrates how to find the largest payment made by each customer. This involves grouping the results by 'customer_id'. This allows us to see the maximum payment made by every individual customer in the dataset.

Query:

SELECT
    customer_id,
    MAX (amount)
FROM
    payment
GROUP BY
    customer_id;

Output

Explanation:

In this query, 'customer_id' is used to group the payments. The MAX(amount) function finds the highest payment for each customer within these groups.

• The MAX() function computes the maximum value over a specified set of values, which can be an entire table or a subset defined by a WHERE clause.
  
• MAX() can be effectively combined with GROUP BY to find maximum values within groups, and with HAVING to filter groups based on aggregate conditions.
  
• Although MAX() operates on a single column, you can include multiple MAX() functions in a single query to find maximum values of different columns.
  
• MAX() ignores NULL values in the computation.

• Use indexes on the columns being queried to improve performance, especially when dealing with large datasets.
  
• Pair the MAX() function with a WHERE clause to narrow down the result set and reduce computation time.

The PostgreSQL MAX() function is an essential tool for analyzing data and identifying maximum values efficiently. By combining it with GROUP BY, WHERE, and HAVING clauses, we can create powerful queries for data aggregation and business requirements. Whether we're working with financial data, timestamps, or text, the MAX() function is a go-to choice for retrieving maximum values quickly and accurately.

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