Appending structures to the tables

Question

Hi experts,
Why we are appending sturctures to the tables?
can any one tell me the main differences between the APPEND and INCLUDE structures
in Datadictionary.
Thanks in Advance.

Answer 1

Hi Ankita,
Customizing Includes
A Customizing include is a structure that satisfies a special naming convention. The name of a Customizing include begins with u2018CI_u2019 and the include is in the customer namespace.
If enhancements are already planned in the R/3 standard using customer-specific fields, such Customizing includes are included. in the corresponding standard table or standard structure. The Customizing include (that is the definition of the structure itself) is usually first created in the customer system and filled with fields by special Customizing transactions.
Customers can thus enhance tables and structures of the R/3 standard system without themselves having to modify the table and structure definitions. This means that these enhancements will not be lost when upgrading. If a table or structure of the R/3 standard system is enhanced with customer fields using a Customizing include, these customer fields are automatically inserted in the new delivered table or structure definition during an upgrade.
If you create a Customizing include for a table or structure, only those enhancements are allowed that are consistent with the enhancement category of the enhanced table or structure. For more information, see Structure Enhancements.
Customers can but need not create a Customizing include and fill it with fields. If there is no Customizing include, there is no error message when the table or structure including it is activated.
A Customizing include can be contained in several tables or structures, so that they remain consistent when the include is modified.
Append Structures
Append structures are used for enhancements that are not included in the standard. This includes special developments, country versions and adding customer fields to any tables or structures.
An append structure is a structure that is assigned to exactly one table or structure. There can be more than one append structure for a table or structure.
The following enhancements can be made to a table or structure TAB with an append structure:
Insert new fields in TAB,
Define foreign keys for fields of TAB that already exist,
Attach search helps to fields of TAB that already exist,
These enhancements are part of the append structure, i.e. they must always be changed and transported with the append structure.
When a table or structure is activated, all the append structures of the table are searched and the fields of these append structures are added to the table or structure. Foreign keys and search help attachments added using the append structure are also added to the table. If an append structure is created or changed, the table or structure assigned to it is also adjusted to these changes when the append structure is activated.
Since the order of the fields in the ABAP Dictionary can differ from the order of the fields on the database, adding append structures or inserting fields in such append structures does not result in a table conversion.
The customer creates append structures in the customer namespace. The append structure is thus protected against overwriting during an upgrade. The fields in the append structure should also reside in the customer namespace, that is the field names should begin with ZZ or YY. This prevents name conflicts with fields inserted in the table by SAP.
Reward if found helpful.
Anirban Bhattacharjee