Nested Structure

Question

I would like to know how to use nested structure in a ABAP program.
Thanks in Advance!

Answer 1

A <b>nested structure</b> is a structure that contains one or more other structures as components.
Flat structures contain only elementary data types with a fixed length
(no internal tables, reference types, or strings).
The term deep structure can apply regardless of whether the structure is nested or not.
Nested structures are flat so long as none of the above types is contained in any nesting level.
Any structure that contains at least one internal table, reference type, or string as a component
(regardless of nesting) is a deep structure.
Accordingly, internal tables, references, and strings are also known as deep data types.
The technical difference between deep structures and all others is as follows:
When you create a deep structure, the system creates a pointer in memory that points to the
real field contents or other administrative information.
When you create a flat data type, the actual field contents are stored with the type in memory.
Since the field contents are not stored with the field descriptions in the case of deep structures,
assignments, offset and length specifications and other operations are handled differently from flat structures.
Kindly check the following link for more information on Nested structures:
http://help.sap.com/saphelp_47x200/helpdata/en/fc/eb2fcc358411d1829f0000e829fbfe/frameset.htm
<b>Examples:</b>
DATA: BEGIN OF itab.
        include structure vbak.  
DATA: END OF itab.
DATA: BEGIN OF itab OCCURS 0,
        itab1 LIKE mara,
        itab2 LIKE vbak,
      END OF itab.
Kindly reward points if it helps!
best regards,
Thangesh