SAP USING KEY documentation, setup help and example usage

INCLUDE
What does it do? The USING KEY addition can be used to specify a table key in keyname used to carry out the processing. The specified table key influences the order in which the table rows are accessed, and the evaluation of the remaining conditions.
If the primary table key is specified, the processing behaves in the same way as when no key is explicitly specified. If a secondary table key is specified, the order in which the rows are accessed is as follows:
Sorted key specified
The rows are processed by ascending row number in the secondary table index

Hash key specified
The rows are processed in the order in which they were inserted into the table.