View Cluster 的优点及创建
View Cluster是一种维护表的方式，不同于一般的View是由于它一般是链接了两个或两个以上有主次关系的表同时进行维护，并且可以保证外键的关系，即次表的主键数据一定要在主表中存在才能创建。
摘抄SAP WIKI中的关于VIEW CLUSTER的优点
Benefits of View Cluster
1) It is easy to maintain data in view clusters because it provides a convenientway of navigation between the maintenance dialogs.
Forexample: User can maintain data in hierarchical manner and hence it is easy tonavigate between the header details and item details.
2) View clusters ensure consistency of the data stored in the tables i.e. copying,deleting, adding and saving the data.
Forexample: If the user wants to delete all the entries of a particular group. Itcan be deleted by deleting the group itself.
Soit would be easy for the user to maintain the data in a consistent manner.
3) N: M relationship can be processed in view clusters. Maintenance dialogs whichdoesn't have any key or have partial key dependency can also be combined intothe view clusters.
创建一个ViewCluster的主要步骤（以2个内表为例）
ZFLX_TABLE01 字段(fielda)
ZFLX_TABLE02 字段(fielda,fieldb)
ZFLX_VIEW01
ZFLX_VIEW02 (注意该视图中的与ZFLX_TABLE01中相同字段得要给字段P赋值S）
详细见SAP WIKI链接 ViewClusters-Creation and its Benefits
