Data Dictionary Views - DDIC views is used to define application-dependent view that combines this data. The data from several tables can be viewed together. The table fields which are not required can be hidden. The views are not physically stored but are derived from one or more table.
There are total four types of views.
Database Views.
Projection Views.
Maintenance Views.
Helps Views.
I. Describe Database Views
This view is implemented with an equivalent view on the database. A database view is automatically created in the underlying database when it is activated. Database views implement an inner join.
Important points to note about database views
- At least one relationship is required.
- No modification can be done. Read only.
- Implements an inner joins.
II. Describe Projection Views
Projection views are used to hide fields of a table. This can minimize interfaces; for example when you access the database, you only read and write the field contents actually needed.
Important points to note about projection views
- It is used for only one table.
- You cannot define selection conditions for projection views.
- Modification (create, delete, insert, and update) can be done.
- You can also access pooled tables & cluster tables with a projection view.
III. Describe Maintenance Views
With Maintenance Views you can also change/edit data. Thus, a maintenance view allows you to maintain the data of an application object together. All the tables in a maintenance view must be linked with foreign key. The join conditions for maintenance views are always derived from the foreign key. You cannot directly enter the join conditions as for database views.
Important points to note about maintenance views
-'N' no. of relationship can support.
- Modification can be done.
- Implements an outer join.
IV. Describe Help Views
Help views can be used in search helps as a selection method. For Example - You may have to create a help view if a view with outer join is needed as selection method of search help.
Important points to note about Help views
- It implements an outer join.