topic Re: generic foreign key in Application Development and Automation Discussions

generic foreign key

Former Member — Thu, 07 Feb 2008 14:03:57 GMT

what are different types of foriegns keys and usages.

Re: generic foreign key

former_member188829 — Thu, 07 Feb 2008 14:25:54 GMT

Hi,

check these links..

http://help.sap.com/saphelp_nw2004s/helpdata/en/cf/21ea84446011d189700000e8322d00/content.htm

http://www.sapdb.org/7.4/htmhelp/ee/1c5bd9eba711d4aa2800a0c9430730/content.htm

Re: generic foreign key

Former Member — Thu, 07 Feb 2008 14:26:43 GMT

good

Foreign key - a foreign key (FK) is a field or group of fields in a database record that points to a key field or group of fields forming a key of another database record in some (usually different) table. Usually a foreign key in one table refers to the primary key (PK) of another table. This way references can be made to link information together and it is an essential part of database normalization

thanks

mrutyun^

Re: generic foreign key

prasanth_kasturi — Fri, 08 Feb 2008 12:17:21 GMT

A foreign key is a field in a table that is connected to another table via a foreign key relationship. The purpose of the foreign key relationship is to validate the data being entered into one table by checking against a valid set of values in another table. The table that contains the foreign key is called the foreign key table. The table that contains the valid set of values is called the check table The field that is validated and on which the foreign key relationship is created is called the foreign key.

A compound foreign key is a foreign key composed of two or more fields. In other words, a check is done to compare two fields in the foreign key table against two fields in the check table. The combination of values must exist in the check table before they can be inserted into the foreign key table. However only one field on the screen will trigger the compound foreign key check.

A generic foreign key is a foreign key in which one of the primary key fields of the check table fields is marked as generic. When a primary key field is marked as generic, it doesn't have a counterpart in the foreign key table, and it does not participate in the check.

Constant foreign keys are compound foreign keys where one of the check table field names is replaced by a constant value. This constant value is entered on the Create Foreign Key screen