Congratulations! You’ve just learned about non-correlated and correlated subqueries in SQL. What can we generalize so far?
- Subqueries are used to complete an SQL transformation by nesting one query within another query.
- A non-correlated subquery is a subquery that can be run independently of the outer query and can be used to complete a multi-step transformation.
- A correlated subquery is a subquery that cannot be run independently of the outer query. The order of operations in a correlated subquery is as follows:
1. A row is processed in the outer query.
2. Then, for that particular row in the outer query, the subquery is executed.