- **Description**: Concatenates the results of subqueries. - **Performance**: Efficient if subqueries are balanced. - **Factors**: Number of subqueries and their costs. - **Cost**: Sum of subquery costs. - ![[assets/ex_append.png|200x200]] - **Operates on**: [[Structures/Result Set]] - **Workloads**: - [[Workloads/IPC]] - [[Workloads/Sub/AppendReady]] - [[Workloads/LWLock]] - [[Workloads/Sub/ParallelAppend]]