Foreign Key

• We can use foreign keys to define relationships between tables in the ABAP Dictionary, create value checks for input fields and link several tables in aview or alock object.
• One of the foreign key fields is marked as the check field. The foreign key relationship is maintained for this field.
• When we make an entry in the check field, the system checks whether the check table contains a record with the key defined by the values in the foreign key fields. 
• If there is such a record, the entry is valid. Otherwise the system rejects the entry.
• Check table is a table which will be connected via foreign key relationship.
• Foreign key of Foreign table must match with the primary key of check table.
• Check table is given at field level.it contains only valid values. 

Steps

• Go to Transaction code SE11.

• Create a Transparent Master Table

• With following fields .

• Enter some records .

• Create a Transparent Transaction Table .

• Make ZSD_VBAP table's VBELN field as foreign key  and ZSD_VBAK table as Check table.
• Select the VBELN field from ZSD_VBAP.

• Click on foreign Key button.

• Pop-up will appear.

• Enter the Check table name.

• Click on Generate proposal.

• Click on Copy button.

• Check the status Bar.

• Click on Save->->Check ->Activate to activate the Table.

Result

• Create records in ZSD_VBAP Table.
• Utilities -> Table Content -> Create Entries.

• VBELN of Table ZSD_VBAP referrers the value of VBELN of ZSD_VBAP.

• Select any value and create record.

• Click on Save.

• Enter some records ,

   

• Other than VBELN value of ZSD_VBAK table , throws error.

                                    more information........