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Relational Databases

Application software models a part of the real world. This type of modeling is based on the relational data model. A data model describes reality using formal structures. In the relational data model, the only formal structure used is known as a relation or table. All the information about the modeled area of reality is represented as values in tables.

A table is a two-dimensional matrix which consists of rows and columns (fields). A field or combination of fields which uniquely identifies every row in a table is known as the key. This is a minimal attribute: if one of the fields is removed from the key, the remaining fields cannot uniquely identify the table rows.

Each table must have at least one table key (primary key integrity). However a table usually has multiple keys. During the modeling process, only one key is defined as the primary key.

In the relational model, the relationship between objects is expressed in terms of a foreign key. A combination of fields in a table is known as a foreign key, if it is also the primary key in another table.

In AS ABAP, the data model is managed in ABAP Dictionary:

  • The database tables and v views of database tables are defined independently of the platform in ABAP Dictionary and are given attributes when they are activated on the central AS ABAP database.
  • The table fields and view fields are components of structures in ABAP Dictionary and are identified accordingly as structured types in ABAP programs.
  • Open SQL statements can be used in ABAP programs to access database tables and views from ABAP Dictionary directly and independently of the platform.

Other versions: 7.31 | 7.40 | 7.54