Summary

In this chapter, you learned that

• A subquery is a query placed within a SELECT , UPDATE , or DELETE statement.

• Single row subqueries return zero or one row.

• Multiple row subqueries return one or more rows.

• Multiple column subqueries return more than one column.

• Correlated subqueries reference one or more columns in the outer SQL statement.

• Nested subqueries are subqueries placed within another subquery.

In the next chapter, you ll learn about advanced queries.