Basics of ABAP : Tables in ABAP/4 dictionary

Tables are the basic objects in R/3 application. There are more than 8000 tables in R/3 system. Following types of tables are available

· Transparent tables

· Pool tables

· Cluster tables

From user point of view, all tables are used to store data whatever be the type of table. There is no difference in the behavior or operation of these tables. All of them can be managed by using standard OPEN SQL. However from an administrator point of view transparent table do exists with the same structure both in the dictionary as well as in the database, exactly with the same data and fields. While other two are not transparent in the sense that they are not manageable directly using database system tools. You can access these tables in R/3 environment from the ABAP/4 dictionary. You cannot use native SQL on these tables. Pool or cluster tables are logical tables, which are arranged as records of transparent table.

A table is made up of rows and columns. When the table is created, its columns are named; data type is supplied for each column. There can be only one data value in each column of each row in a table. Record or as it is called in different RDBMS is nothing but group of fields. While a column is a field of a table, a table is an indexed file. The main index is called as primary key, which can be a single field or combination of keys or fields. A primary key can be defined as a field, which indefinites a single unique record of the table. A table cannot have record with duplicate primary key. 

In any RDBMS, tables are related to each other. But to relate table to each other it is necessary that one of the tables contain some information of other table. Mostly tables are related to each other through primary keys. The primary key of one table, if it exists in other table then it is called foreign key. This type of database management system means that there is some redundancy of data. But using normalization procedures available can minimize it. One of the most important functions of foreign key is to ensure data integrity. For example say you have EMP table, which has fields: emp.no., emp.name, dept.code, salary and you have DEPT tables, which has dept.code and dept.desc. Then in DEPT table dept.code is primary key while dept.code in EMP table is foreign key. If you enter dept.code for particular

employee in EMP table the dept.code should exist in DEPT table. System will check the value for dept.code in DEPT table, and if does not exist then will flash error. In this case DEPT is called check table while EMP is foreign key table.

Creation of table
Steps to create a table
¨ Create domain
¨ Create data element
¨ Create actual table