Show All Rows with an Above-Average Value in PostgreSQL

PostgreSQL is a robust relational database management system that offers powerful features for data analysis. One common task in data analysis is identifying rows with values above the average of a specific column.

In this article, we will explore how to Show All Rows with an Above-Average Value in PostgreSQL by understanding the multiple approaches with the help of examples and so on.

When working with databases, it is often necessary to filter rows based on certain conditions. In this case, we want to show all rows where a specific column value is above the average of that column. PostgreSQL provides several methods to solve this problem. below are the methods that help us to show All Rows with an Above-Average Value in PostgreSQL are as follows:

1. Using Subqueries
2. Using a Window Function
3. Using a Common Table Expression (CTE)

Let’s set up an environment

To understand how to Show All Rows with an Above-Average Value in PostgreSQL we need a table on which we will perform various operations and queries. Here we will consider a table called sales_data with columns transaction_id, product_name, and amount to represent sales transactions:

CREATE TABLE sales_data (
    transaction_id SERIAL PRIMARY KEY,
    product_name VARCHAR(100),
    amount NUMERIC
);

Now, let’s insert some sample data into this table:

INSERT INTO sales_data (product_name, amount) VALUES
    ('Product A', 1500),
    ('Product B', 2200),
    ('Product C', 1800),
    ('Product D', 1300),
    ('Product E', 2500);

Output:

Let’s Retrieve all records from the sales_data table where the amount is greater than the average amount in the sales_data table.

SELECT *
FROM sales_data
WHERE amount > (SELECT AVG(amount) FROM sales_data);

Output:

Explanation: This query retrieves all columns from the sales_data table for rows where the amount is greater than the average amount in the sales_data table.

Let’s Retrieve all records from the sales_data table where the amount is greater than the average amount in the sales_data table for each row

SELECT *
FROM (
    SELECT *,
           AVG(amount) OVER () AS average_amount
    FROM sales_data
) AS subquery
WHERE amount > average_amount;

Output:

Explanation: This query calculates the average amount from the sales_data table using the AVG window function and then selects all columns from the sales_data table where the amount is greater than this average amount.

Let’s Retrieve all records from the sales_data table where the amount is greater than the average amount calculated using a Common Table Expression (CTE) named average_cte

WITH average_cte AS (
    SELECT AVG(amount) AS average_amount
    FROM sales_data
)
SELECT *
FROM sales_data
JOIN average_cte ON true
WHERE amount > average_amount;

Output:

Explanation: This query calculates the average amount from the sales_data table using a Common Table Expression (CTE) named average_cte and then joins the sales_data table with the average_cte to filter and select all rows where the amount is greater than the average amount.

Overall, In this article, we have understand the three approaches to showing all rows with an above-average value in PostgreSQL. By using the method like subqueries, window functions, and Common Table Expressions you can efficiently filter rows based on specific conditions and gain valuable insights from your data.