Database Views

A view is a logical window to a table or more than one table, the data from a view is not actually physically stored instead being derived from one or more tables. A view can be used to summarize data which is distributed among several tables. It does not contain memory space. During runtime it contains memory after the execution the memory will be released

Types of Views

1. Projection View
2. Database View
3. Maintenance View
4. Help View

Projection View: This view is used to display data’s from only one table i.e. view can draw upon only one table, this means that only the data that actually required is exchanged when the database is accessed. Selection conditions cannot be specified for projection view.

Database View: This view is used to display data’s from more than one table. Database views are implement an inner join, that is, only records of the primary table for which the corresponding records of the secondary tables also exist are fetched. In database views, the join conditions can be formulated using equality relationships between any base fields. Inconsistencies between primary and secondary table could, therefore, lead to reduced selection set.

Maintenance View: This view is used to for data manipulation like insert, update, delete, modify etc. Data from several tables can be summarized in a maintenance view and maintained collectively via this view. That is the data is entered via the view and then distributed to the underlying tables by the system.

Help View: This view is used to displaying possible values of field from one or more than one table i.e. used to output additional information when the online help system is called or when F4 is pressed on the field.