SQL Count Duplicates: GROUP BY & COUNT

In SQL, GROUP BY and COUNT functions can be used to calculate the number of repeated occurrences. Here is an example:

If there is a table called “orders” with a column named “product_id”, we can use the following SQL query to calculate the frequency of each product appearing.

SELECT product_id, COUNT(*) AS count
FROM orders
GROUP BY product_id

The above query groups orders by product ID and calculates the frequency of each product ID. The COUNT function is used to calculate the number of rows in each group, resulting in the occurrences of each product ID.