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Transparent | Pool | Cluster |
Contain a single table. Used to store master data | They are used to hold a large number of very small tables(stores customizing data or system data) | They are used to hold data from a few number of large tables.(stores system data) |
It has a one-to-one relationship with a table in the database | It has a many-to-one relationship with a table in the database | It has a many-to-one relationship with table in the database |
For each transparent table there is one associated table in the database | It is stored with other pooled tables in a single table called table pool in the database | Many cluster tables are stored in a single table in the database called a table cluster |
The database table has the same name, same number of fields and the fields have the same names | The database table has different name, different number of fields and fields have different names | The database table has different name, different number of fields and fields have different names |
There is only a single table | Table pools contain more tables than table clusters | Contains less tables than table pools |
Single table can have one or more primary key | Primary key of each table does not begin with same fields or fields | Primary key of each table begins with same fields or fields |
Secondary indexes can be created | Secondary indexes cannot be created | Secondary indexes cannot be created |
They can be accessed using open and native SQL | They can be accessed using open SQL only | They can be accessed using open??SQL only |
USE: They are used to hold master data e.g. Table vendors or table of customers. Example of transaction data is orders placed by customers | USE: They reduce the amount of database resources needed when many small tables have to be opened at the same time | USE: They would be used when the tables have primary key in common and data in these tables are all accesses simultaneously |
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From <http://saptechnical.com/Tutorials/ABAP/Pool/Index.htm>
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原文地址:http://www.cnblogs.com/rootbin/p/4463461.html