SQL MAX() and MIN() Functions

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When working with databases, there are times when you need to find the largest or smallest value within a column. Whether you're analyzing sales figures, employee salaries, or product prices, the SQL MAX() and MIN() functions provide a quick and efficient way to retrieve these values.

These functions are part of SQL’s aggregate functions and are typically used with the SELECT statement to return the maximum and minimum values in a dataset. In this blog post, we’ll explore how the MAX() and MIN() functions work, with examples to demonstrate their practical usage.

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1. SQL MAX() Function: Retrieving the Maximum Value

The MAX() function in SQL is used to return the largest value from a specified column. It is commonly used for numeric, date, or string data types, depending on what you are analyzing.

Syntax:

SELECT MAX(column_name)
FROM table_name;

• column_name: The column from which you want to retrieve the maximum value.

Example:

Suppose you have a sales table that contains the amount column representing the amount of each sale, and you want to find the largest sale made.

SELECT MAX(amount) AS largest_sale
FROM sales;

Result:

largest_sale
5000

This query returns the largest sale amount from the sales table.

Important Consideration:

• MAX() works with numeric, date, and string data types.
• If the column contains NULL values, they are ignored in the calculation.

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2. SQL MIN() Function: Retrieving the Minimum Value

The MIN() function in SQL is used to return the smallest value from a specified column. Like the MAX() function, MIN() can be used with numeric, date, or string data types.

Syntax:

SELECT MIN(column_name)
FROM table_name;

• column_name: The column from which you want to retrieve the minimum value.

Example:

Suppose you want to find the smallest sale amount in the sales table.

SELECT MIN(amount) AS smallest_sale
FROM sales;

Result:

smallest_sale
100

This query returns the smallest sale amount from the sales table.

Important Consideration:

• MIN() also works with numeric, date, and string data types.
• Like MAX(), MIN() ignores NULL values when calculating the result.

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3. Using MAX() and MIN() with Other Columns

While MAX() and MIN() are often used to find the highest or lowest value in a column, you can also use them with other columns in combination with GROUP BY to find the maximum or minimum value for each group.

Example with GROUP BY:

Suppose you have an employees table with columns department and salary, and you want to find the highest and lowest salary in each department.

SELECT department, MAX(salary) AS highest_salary, MIN(salary) AS lowest_salary
FROM employees
GROUP BY department;

Result:

department	highest_salary	lowest_salary
Sales	80000	45000
Marketing	75000	50000
Engineering	95000	60000

This query groups employees by their department and returns the highest and lowest salary for each department.

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4. Using MAX() and MIN() with Dates

The MAX() and MIN() functions are also useful for working with date columns. You can use them to find the most recent or oldest record in a table.

Example with Dates:

Suppose you have an orders table with an order_date column, and you want to find the most recent and the oldest order dates.

SELECT MAX(order_date) AS latest_order, MIN(order_date) AS earliest_order
FROM orders;

Result:

latest_order	earliest_order
2024-12-20	2023-01-01

This query returns the latest and earliest order dates in the orders table.

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5. Combining MAX() and MIN() with Other Functions

You can combine the MAX() and MIN() functions with other aggregate functions for more complex queries. For example, you might want to find the maximum and minimum order values along with the total sum of sales.

Example:

Suppose you want to find the total sales, highest sale, and lowest sale in the sales table.

SELECT SUM(amount) AS total_sales,
       MAX(amount) AS largest_sale,
       MIN(amount) AS smallest_sale
FROM sales;

Result:

total_sales	largest_sale	smallest_sale
150000	5000	100

This query returns the total sales, the largest sale, and the smallest sale in the sales table.

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6. NULL Values in MAX() and MIN()

As mentioned earlier, the MAX() and MIN() functions ignore NULL values. This means that if a column contains NULL values, they will not affect the result.

Example:

Suppose the amount column in the sales table contains some NULL values. If you use MAX() or MIN(), the NULL values are automatically excluded.

SELECT MAX(amount) AS largest_sale
FROM sales;

If the amount column has NULL values, they will not be considered in the calculation of the largest value.

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7. Using MAX() and MIN() in Subqueries

You can also use the MAX() and MIN() functions in subqueries to filter records based on these values.

Example with Subquery:

Suppose you want to find all sales that are equal to the highest sale in the sales table.

SELECT sale_id, amount
FROM sales
WHERE amount = (SELECT MAX(amount) FROM sales);

Result:

sale_id	amount
1001	5000

This query uses a subquery to find the largest sale and retrieves the sale_id and amount for that sale.

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