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4 cards from this section. Quick, good the night before a test.
What is a subquery?
Think of it as a query within a query.
Which clause often contains subqueries?
It filters results based on criteria.
What is a subquery?
Think about how queries can be structured within one another.
Do subqueries always perform better than JOINs?
When do you think performance might be affected?
Construct a query to find product IDs for products that have been sold in orders totaling more than $500, using a subquery.
Use SUM in the subquery to aggregate data.
Write a SQL statement to find users who have not made any purchases. Use a subquery to achieve this.
Think about how to filter users based on absence in the orders.
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