Structure & view

Question

what is the difference between structure & view.
pls answer this question,
amruth.

Answer 1

Hi Amruth,
Structures
A structure is a user-defined sequence of data types.
It fully defines the data object.
You can either access the entire data object, or its individual components. ABAP has no predefined
structures. You therefore need to define your own structures, either in the ABAP program in
which you want to use it, or in the ABAP Dictionary.
You use structures in ABAP programs to group work areas that logically belong together.
Since the individual elements within a structure can be of any type, and can also themselves be
structures or internal tables, the possible uses of structures are very wide-ranging. For example,
you can use a structure with elementary data types to display lines from a database table within a
program. You can also use structures containing aggregated elements to include all of the
attributes of a screen or control in a single data object.
<b>Views:</b>
Views
By defining views, logical views permitting access to certain data can be created specially for the application. The structure of such a view is defined by specifying the tables and fields used in the view.
A view can be used to combine the data distributed in several tables. Fields which are not required can be masked out, minimizing interfaces.
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.
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 copy the join condition from foreign key defined between the tables. In the third step, you must select the fields of the base tables to be used in the view. Selection conditions which restrict the records in the view can be formulated in the fourth step.
Four different types of view 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 are implemented with an equivalent view on the database.
      Projection Views are used to mask out fields from the tables (only projection).The R/3 System implements the access to the base tables.
      Help Views can be used as selection method in Search Helps.
      Maintenance Views are used for business-oriented views on data. Access to the base tables is implemented using a special maintenance module which can be generated automatically from the view definition.
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 into a maintenance view or help view if they are linked to one another with foreign keys.
The Maintenance Status defines whether you can only read the view or whether the view data can also be maintained.
See also:
Join, Projection and Selection
Inner and Outer Join
Creating Views
Changing Views
Deleting Views
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Cheers,
Chaitanya.