ABAP Dictionary Views and their types

Views are generally virtual tables that are created in Data Dictionary as a cross product of a multiple tables as a projection of one table.  The views are used to look into one or more tables.

A view does not contain data of its own.

Types of Views

          1) Database View : The database view is the only type of view in SAP that is physically created at the database level.  In other words, the underlying database system also directly recognizes the view, apart from SAP.  Therefore, database views must be created over transparent tables. With the database view, all three of the relational operations (projection, selection, and join) can be used. Database views can be buffered just like transparent tables.  In the technical settings you can decide whether to have buffering off, or on with type single record, generic, or full. 

          2) Projection View : The projection view is a logical view.  In this context, the word "logical" means that the view exists within the ABAP Dictionary but is not recognized by the underlying database system. Projection views must be defined over a single transparent table. The only relational operators that is valid for a projection view is a projection.

          3) Maintenance View : These views permit maintenance of base table data.  Transactions SM30 and SE54 are provided for working with maintenance views.

          4) Help View : Help views can be used as selection methods for Search Helps. It might be necessary to create a Help View if you are trying to accomplish an outer join, since database views only create inner joins.

View - Maintenance Status

The maintenance status of a view controls whether data records can also be changed or inserted in the tables contained in the view.

The maintenance status can be defined as follows:

        - Read only: Data can only be read with the view.

        - Read, change, delete and add: Data of the tables contained in the     view can be changed, deleted and inserted with the view.

Only read access is permitted for database views that are defined over several tables. If a database view contains only one single table, data can be inserted into this table with the view.

The following status definitions are possible for maintenance views

      - read and change: Existing view entries can be changed. Records cannot be deleted or inserted.

      - Read and change (time-dependent views) : Only entries whose non-time-dependent part of the key is the same as that of existing entries may be inserted.