New SQL Codes for Query

  • The WITH statement allows us to perform a separate query (such as aggregating customer’s subscriptions)
  • previous_query is the alias that we will use to reference any columns from the query inside of the WITH clause
  • We can then go on to do whatever we want with this temporary table (such as join the temporary table with another table)

Essentially, we are putting a whole first query inside the parentheses () and giving it a name. After that, we can use this name as if it’s a table and write a new query using the first query.


WITH previous_query AS(SELECT customer_id,
COUNT(subscription_id) AS 'subscriptions'
FROM orders
GROUP BY customer_id)

SELECT customers.customer_name,previous_query.subscriptions
FROM previous_query
JOIN customers
ON previous_query.customer_id = customers.customer_id;

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