Data about an application object is often distributed on several tables. By defining a view, you can define an application-dependent view that combines this data. The structure of such a view is defined by specifying the tables and fields used in the view. Fields that are not required can be hidden, thereby minimizing interfaces. A view can be used in ABAP programs for data selection.
The data of a view is derived from one or more tables, but not stored physically. The simplest form of deriving data is to mask out one or more fields from a base table (projection) or to include only certain entries of a base table in the view (selection). More complicated views can comprise several base tables, the individual tables being linked with a relational join operation. See alsoJoin, Projection and Selection.
The base tables of the view must be selected in the first step of a view definition. In the second step, these tables must be linked by defining the join conditions. It is also possible to use the join condition from a foreign key defined between the tables (seeForeign Key Relationship and Join Condition). In the third step, you must select the fields of the base tables to be used in the view. Selection conditions that restrict the records in the view can be formulated in the fourth step.
Four different view types are supported. These differ in the way in which the view is implemented and in the methods permitted for accessing the view data.
Database views implement an inner join. The other view types implement an outer join (seeInner and Outer Join).
The join conditions for database views can be formulated using equality relationships between any base fields. The join conditions for the other view types must be obtained from existing foreign keys. Tables therefore can only be combined in a maintenance view or help view if they are linked to one another with foreign keys.
Themaintenance status defines whether you can only read data with the view or whether you can also insert and change data with it.
See also:Example for Views Creating Views Deleting Views