Chapter 08 abap dictionary objects views1

ABAP Dictionary Objects: Views

March-2005ABAP Dictionary Objects: Views |

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Objectives

• The participants will be able to: – Define a View.– Explain the different Relational Operations.– Discuss the different types of Views.– Discuss how to use Views in an ABAP program.


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What is a View?


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Views are used to look into one or more tables.

A view does not contain data of its own.

The Most Basic Form of a View


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In its most basic form, a view simply mirrors an entire database table

The Relational Operations


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Table 2

Selection

View BView B

Table 1

Projection

View AView A View CView C

Join

Table 4Table 4Table 3Table 3

We can use views to Join several tables, Project (or choose) certain fields from one or more tables & Select (or choose) certain records from one or more tables.

The Projection Operation


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Projection

View AView A

Table 1

The projection operation is used to narrow a view’s focus to certain fields in a table.

Specifying Projected Fields


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Can use any field name if database view, otherwise must be same name as table field.

The Selection Operation


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Selection

View BView B

Table 2

Example:Staff Level <= 3

The selection operation is used to narrow a view’s focus to certain records in a table.

Specifying Selection Criteria


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1 2 3 4 5

Can include unprojected fields

The Join Operation


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Table 3Table 3Join

Table 4Table 4

View CView C

The join operation is used to combine information from multiple tables into a single view.

The Necessity of the Join Operation


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Salary

ID Name Salary

5579 Smith $10,000.00

5579 Smith $11,000.00

5579 Smith $12,000.00

5579 Smith $13,000.00

ID Name Salary 1 Salary 2 Salary 3 …

Employee

Wrong

Database design principles often require related data to be stored in separate tables. This is called normalising.

Understanding the Join Operation


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ID Name …

EmployeeEmployee

ID Salary Date Effective

5579 $10,000.00 10/1/91

5579 $11,000.00 10/1/92

5579 $12,000.00 10/1/94

5579 $13,000.00 10/1/96

SalarySalary

Right

The join operation essentially reverses the normalising process.

The result of a join is a view that looks like a table with redundant data.

The Join Operation and Foreign Keys


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View CView C

Join

Table 4Table 4Table 3Table 3Primary Secondary

Therefore, in order to use the join operation in SAP, you must first ensure that the appropriate foreign key relationships exist among the tables to be joined.

Specifying Joined Fields


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Indicate base tables that data will come from.Indicate base tables that data will come from.

Hit button to see related tables and automatically generate join conditions.

Join Conditions

Types of Views in the ABAP Dictionary

• Database View• Projection View • Help View• Maintenance View


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The Database View


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Database

DB

Database View

The database view is the only type of view in SAP that is physically created at the database level.

Demonstration

• Creation of a database view using two related database tables.


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Practice

• Creation of a database view using two related database tables.


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The Projection View


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View C

Projection View

The projection view is a logical view. In this context, the word “logical” means that the view exists within the ABAP Dictionary but is not recognized by the underlying database system.

Database vs. Projection Views


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Database ViewProjection View

• Must be built over a single table• Data can be updated• Data updates must use open SQL• Updates are less efficient • Fields in the view must be named the same as the fields in the underlying table• Can’t be buffered

• Can be built over many tables• Data can be updated if the view is built over a single table• Data updates can use open or native SQL• Updates are more efficient • Fields in the view can be named differently from the fields in the underlying table• Can be buffered

Other Types of Views

• Help View: Help views can be used as selection methods for Search Helps.It might be necessary to create a Help View if you are trying to accomplish an outer join.

• Maintenance View: These views permit maintenance of base table data. Transactions SM30 and SE54 are provided for working with maintenance views.


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Using a View in Program Code


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TABLES: YXXEMP_V.

SELECT*FROM YXXEMP_V.

WRITE: / YXXEMP_V-EMP_IDYXXEMP_V-LAST_NAME,YXXEMP_V-FIRST_NAME.

ENDSELECT.

Demonstration

• Select data from the database view created earlier and display selected data in a report.


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Practice

• Select data from the database view created earlier and display selected data in a report.


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Summary• Views are used to look into one or more tables. A view does not contain

data of its own.• The projection operation is used to narrow a view’s focus to certain fields

in a table.• The Selection Operation is used to narrow a view’s focus to certain

recordsin a table.

• The Join Operation is used to combine information from multiple tables into a single view.

• Types of Views in the ABAP Dictionary are Database View, Projection View, Help View & Maintenance View.

• The syntax to reference a view in an ABAP program is the same syntax we use to reference a table.


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Questions

• What is a View ?• What is a Database view ?• What is a Projection view ?• What is a Maintenance view ?• What is a Help view ?


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Documents

Chapter 08 abap dictionary objects views1