SAP ITAB KEY SECONDARY DUPLICATES

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ABAP_ITAB - Duplicate Non-Unique Keys
Non-unique table keys can produce duplicate lines with respect to these keys. This section describes the order of these duplicates when inserting into tables with non-unique sorted table keys. This order is ignored with respect to non-unique primary keys in standard tables.
ITOC

Single Record Operations
When individual lines are inserted where the insert position is determined using a table key, that is, in the case of

the operations INSERT ... INTO TABLE ... or

in lazy updates of sorted secondary keys
the order of the duplicates with respect to the table key of the target table is determined in accordance with the insertion order of the individual lines. The duplicate line that was last inserted into the table is sorted before all other duplicates.

Block Operations
For block operations such as an assignment of an internal table to another table or when inserting multiple lines using INSERT LINES OF, the order of duplicates with respect to a sorted key of the target table in the block is taken from the source table. If there are already one or more duplicates in the target table, the source block duplicates are inserted in their original order in front of the first duplicate in the target table.

Special Features
Some operations have the characteristics of block operations but are executed internally as sequences of single record operations. In this case, the original order of duplicates with respect to a sorted key in the target table is not retained. This is the case for the following operations:

Filling an internal table using IMPORT from a table previously stored using EXPORT and all operations that are based internally on such an import, such as posting operations.
BEGIN_SECTION VERSION 5 OUT

Passing and inheriting internal tables for Remote Function Calls.
END_SECTION VERSION 5 OUT

The deserialization of an internal table from a table previously serialized to XML using CALL TRANSFORMATION.

ABAP_EXAMPLE_VX5
The result of the following insertion is a a
b z
b y
b x
b b
ABEXA 01062
ABAP_EXAMPLE_END