Views

View :

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.

Types of views:

– Database View (SE11)

Database views are implement an inner join, that is, only records of the primary table (selected via the join operation) for which the corresponding records of the secondary tables also exist are fetched. Inconsistencies between primary and secondary table could, therefore, lead to a reduced selection set.

In database views, the join conditions can be formulated using equality relationships between any base fields. In the other types of view, they must be taken from existing foreign keys. That is, tables can only be collected in a maintenance or help view if they are linked to one another via foreign keys.

 – Help View ( SE54)

Help views are used to output additional information when the online help system is called.

When the F4 button is pressed for a screen field, a check is first made on whether a matchcode is defined for this field. If this is not the case, the help view is displayed in which the check table of the field is the primary table. Thus, for each table no more than one help view can be created, that is, a table can only be primary table in at most one help view.

 – Projection View

Projection views are used to suppress or mask certain fields in a table (projection), thus minimizing the number of interfaces. This means that only the data that is actually required is exchanged when the database is accessed.

A projection view can draw upon only one table. Selection conditions cannot be specified for projection views.

 – Maintenance View ( SE54 )

Maintenance views enable a business-oriented approach to looking at data, while at the same time, making it possible to maintain the data involved. 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.

Inner join

The data that can be selected with a view depends primarily on whether the view implements an inner join or an outer join. With an inner join, you only get the records of the cross-product for which there is an entry in all tables used in the view. With an outer join, records are also selected for which there is no entry in some of the tables used in the view.  The set of hits determined by an inner join can therefore be a subset of the hits determined with an outer join.

Example for Inner join:

SELECT A~EBELN A~LIFNR A~KNUMV B~EBELP B~NETWR B~NETPR B~WERKS B~MATNR
L~NAME1 L~NAME2
FROM EKKO AS A
INNER JOIN EKPO AS B ON A~EBELN = B~EBELN
INNER JOIN LFA1 AS L ON L~LIFNR = A~LIFNR
* INNER JOIN EKKN AS C ON C~EBELN = A~EBELN
INTO CORRESPONDING FIELDS OF TABLE itab
WHERE B~BUKRS = ‘company code’ .

Left outer join
Usually, when defining InfoSets, the objects are linked via inner join operators. However, you can also use left outer joins.  Inner join and left outer join are only different in the situation where one of the involved tables does not contain any suitable record which meets the join conditions.

With an inner join (table 1 inner join table 2), no record is included in the result set in this case. However, this means that the corresponding record from tables 1 is not considered in the results set.

With an left outer join (table 1 left outer join table2), exactly one record is included in the results set in this case´. In this record, the fields from table 1 contain the values of the record from table 1 and the fields from table 2 are all filled with the initial value.

Inner Join and Outer Join 

The data that can be selected with a view depends primarily on whether the view implements an inner join or an outer join. With an inner join, you only get the records of the cross-product for which there is an entry in all tables used in the view. With an outer join, records are also selected for which there is no entry in some of the tables used in the view.

The set of hits determined by an inner join can therefore be a subset of the hits determined with an outer join.

Database views implement an inner join. The database therefore only provides those records for which there is an entry in all the tables used in the view. Help views and maintenance views, however, implement an outer join.