Playing with SQL on the IBM i System: IBM-i Aggregate Functions

In the world of data management, SQL (Structured Query Language) stands out as a powerful tool for querying and manipulating databases. Among its many features, aggregate functions are some of the most valuable yet often underutilized capabilities. These functions allow you to perform calculations on multiple rows of data, returning a single value. Let’s dive into the world of SQL’s aggregate functions, specifically within the IBM-i environment.

What Are Aggregate Functions?

Aggregate functions perform a calculation on a set of values and return a single value. They are commonly used with the ‘GROUP BY’ clause in SQL statements to group rows that have the same values in specified columns into summary rows.

Here are some of my most commonly used aggregate functions:

• SUM(): Adds up all the values in a specified column.
• COUNT(): Counts the number of rows in a specified column.
• AVG(): Calculates the average of a group of selected values.
• MIN(): Finds the minimum value in a specified column.
• MAX(): Finds the maximum value in a specified column.

Why Use Aggregate Functions?

Aggregate functions are essential for data analysis and reporting. They help in summarizing large datasets, making it easier to extract meaningful insights. For instance, you can quickly determine the total sales for a month, the average salary of employees in a department, or the highest and lowest scores in a test.

Examples of Aggregate Functions in IBM-i SQL

Let’s explore some practical examples of how these functions can be used in an IBM-i environment.

1. Calculating Total Sales
   SELECT SUM(sales_amount) AS total_sales FROM sales_data;
   This query calculates the total sales from the ‘sales_data’ table.
2. Counting the Number of Employees
   SELECT COUNT(employee_id) AS total_employees FROM employees;
   This query counts the number of employees in the ’employees’ table.
3. Finding the Average Salary
   SELECT AVG(salary) AS average_salary FROM employees;
   This query calculates the average salary of employees.
4. Determining the Minimum and Maximum Scores
   SELECT MIN(score) AS lowest_score, MAX(score) AS highest_score FROM test_scores;
   This query finds the lowest and highest scores from the ‘test_scores’ table.
   Advanced Usage: Combining Aggregate Functions with ‘GROUP BY‘

The true power of aggregate functions is unleashed when combined with the ‘GROUP BY’ clause. This allows you to perform calculations on subsets of data.

For example, to find the total sales for each product category:

SELECT category, SUM(sales_amount) AS total_sales
FROM sales_data
GROUP BY category;

This query groups the sales data by category and calculates the total sales for each category.

Love me some Aggregates!

Aggregate functions are indispensable tools in SQL, especially within the IBM-i environment. They simplify complex data analysis tasks, allowing you to derive valuable insights from your data with minimal effort. By mastering these functions, you can unlock the full potential of SQL and make your data work for you.

Whether you’re a seasoned SQL user or just starting, exploring these hidden gems will undoubtedly enhance your data management skills. Happy querying!