SQL Group By vs Distinct

Difference between GROUP BY and DISTINCT

GROUP BY is used in combination with aggregation functions. Consider the following table:

The query below uses GROUP BY to perform aggregated calculations.

SELECT
    storeName,
    COUNT(*) AS total_nr_orders,
    COUNT(DISTINCT userId) AS nr_unique_customers,
    AVG(orderValue) AS average_order_value,
    MIN(orderDate) AS first_order,
    MAX(orderDate) AS lastOrder
FROM
    orders
GROUP BY
    storeName;

and will return the following information

While DISTINCT is used to list a unique combination of distinct values for the specified columns.

SELECT DISTINCT
    storeName,
    userId
FROM
    orders;