What is a check table and What is a value table?
The relational data model contains not only tables, but also relationships between tables. These relationships are defined in the ABAP/4 Dictionary by foreign keys. An important function of foreign keys is to support data integrity in the relational data model. Foreign key fields may assume only those values allowed by the check table, in other words, values occurring in the primary key of the check table.
A foreign key provides a link between two tables, for eg.,T1 and T2 by including a reference in table T1 to the primary key of table T2. For this purpose, Foreign key fields assigned to the primary key fields of T2 are included in T1. Table T1, which is the one being checked, is called a foreign key table, and table T2 is called a check table. The terms dependent (foreign key) table and referenced (check) table are also used.
VALUE TABLE:If the domain of the check field has a value table, this is proposed by the system as check table in the foreign field maintenance. The key fields of the value table are in this case assigned fields of the foreign key table with the same domain. These fields may assume only those values allowed by the value table.
The value range of the domain can be defined by specifying value table.All table fields referring to this domain can then be checked against the corresponding field of this value table.In order the check can be executed, a foreign key must be defined for the value table.
What are matchcodes? Describe?
A matchcode is a tool to search for data records in the system. Matchcodes are an efficient and user-friendly search aid for cases where the key of a record is unknown.
It consists of two stages one is Match code object and the other is Matchcode ID.
A matchcode object describes the set of all possible search paths for a search term.
Matchcode ID describes a special search path for a search term.
What are ranges? What are number ranges?
It is often necessary to directly access individual records in a data structure. This is done using unique keys. Number ranges are used to assign numbers to individual database records for a commercial object, to complete the key. Such numbers are e.g. order numbers or material master numbers.
