9.1. What Is a Subquery?9.2. Subquery Types9.3. Noncorrelated Subqueries9.3.1. Multiple-Row, Single-Column Subqueries9.3.1.1. The in operator9.3.1.2. The all operator9.3.1.3. The any operator9.3.2. Multicolumn Subqueries9.4. Correlated Subqueries9.4.1. The Exists Operator9.4.2. Data Manipulation Using Correlated Subqueries9.5. When to Use Subqueries9.5.1. Subqueries as Data Sources9.5.1.1. Table fabrication9.5.1.2. Task-oriented subqueries9.5.2. Subqueries in Filter Conditions9.5.3. Subqueries as Expression Generators9.6. Subquery Wrap-up9.7. Exercises9.7.1. 9-19.7.2. 9-29.7.3. 9-39.7.4. 9-4