The most Important thing I missed in this video since I can't edit this video now: that we are calculating lv_max_booking/max_booking_suppl_id two time:-
For the first time using the read entities statement, we read the data from the transactional buffer for this travel for all bookings ( in transactional buffer always have DB data + additional data which the user creates during this session) .
The second time from importing parameter entities this will be useful in the case of the draft scenario as of now you can ignore what will be explained in the draft.

Playlist
RAP:-
   • Introduction to ABAP RESTful Applicat...  

OData:-
   • OData a Restful API SAP ABAP Part 1  

SAP ABAP on HANA course :-
   • SAP ABAP on HANA Introduction Part 1 ...  

ABAP SAP ABAP 7.4 / 7.5 New Syntax:-
   • New And Value Operator in ABAP 7.4 / ...  

Enhancement in ABAP:-
   • SAP Enhancement Framework ( Implicit ...  

CDS in ABAP on HANA :-
   • SAP CDS Introduction -Part 1 ABAP on ...