ABAP DATA SECONDARY KEY Statement syntax and functionality in SAP

DATA - secondary_key

Short Reference

ABAP Syntax ... {UNIQUE HASHED}|{UNIQUE SORTED}|{NON-UNIQUE SORTED}
KEY key_name COMPONENTS comp1 comp2 ... .

What does it do? Defines a secondary table key of an internal table. The syntax and semantics of the additions are the same as those for the
TYPES statement for standalone table types.

ABAP_PGL Use secondary keys in a way that benefits the table.
Latest notes: When internal tables are accessed with the statements READ TABLE itab ,
LOOP AT itab , MODIFY itab , and DELETE itab or using table expressions , a secondary key can be used to determine the rows to be processed or the processing order. To do this, the additions WITH [TABLE] KEY ... COMPONENTS or
USING KEY must be specified in the statements and KEY in table expressions. A secondary key is never used implicitly.
The INSERT itab statement determines the insert position using the primary key and primary index only. A secondary key can be specified only for the source table from which multiple rows are copied. The latter also applies to the APPEND statement.
If a secondary key is defined, the addition
WITH HEADER LINE can no longer be specified, even outside classes.
For more information, see TYPES
.
Example ABAP Coding The DEMO_SECONDARY_KEYS
program demonstrates the declaration and use of a secondary table key and the resulting performance gains.

ABAP DATA SECONDARY KEY Statement syntax, information and example SAP source code