Lesson 5 Practice — Booking Associations

In Lesson 4 practice, you solved the booking problem with explicit joins. The guided Lesson 5 material now provides the association concepts you will apply here.

Now solve the same kind of problem with reusable CDS relationships.

Your architecture will be:

text

/DMO/BOOKING
      ↓
ZI_BOOKING_ASSOC_###
      ├── _Customer ───► /DMO/I_CUSTOMER
      ├── _Carrier ────► /DMO/I_CARRIER
      └── _Connection ─► /DMO/I_CONNECTION
              ↓
       Booking Reader
              ↓
           Runner

The complete solution is intentionally not included here.

Objects to create

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ZI_BOOKING_ASSOC_###
ZCL_BOOKING_ASSOC_READER_###
ZCL_CDS_L05_PRACTICE_###

Optional challenge:

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ZI_CARRIER_CONNECTIONS_###

Replace ### with your student/group suffix.

Part 1 — Inspect the target CDS entities

Open each target using:

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Ctrl + Shift + A

Inspect:

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/DMO/I_CUSTOMER
/DMO/I_CARRIER
/DMO/I_CONNECTION

Record the keys.

`/DMO/I_CUSTOMER`

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Key:

`/DMO/I_CARRIER`

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Key:

`/DMO/I_CONNECTION`

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Key field 1:
Key field 2:

Do not continue until you know the complete key of /DMO/I_CONNECTION.

Part 2 — Inspect `/DMO/BOOKING`

Open:

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/DMO/BOOKING

Identify:

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travel_id
booking_id
booking_date
customer_id
carrier_id
connection_id
flight_date
flight_price
currency_code

Confirm the booking key:

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travel_id + booking_id

Part 3 — Plan the relationships

Complete:

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Booking.customer_id
    → ______________________________

Booking.carrier_id
    → ______________________________

Booking.carrier_id + Booking.connection_id
    → ______________________________

For each relationship, decide:

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to-one or to-many?

Write a one-sentence reason for each answer.

Part 4 — Create `ZI_BOOKING_ASSOC_###`

Create a Data Definition.

Use:

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Name:        ZI_BOOKING_ASSOC_###
Description: Lesson 5 - Booking Associations

Choose a CDS View Entity template.

Primary source:

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/DMO/BOOKING

Alias:

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Booking

Part 5 — Build the base model first

Before adding associations, expose:

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TravelId
BookingId
BookingDate
CustomerId
CarrierId
ConnectionId
FlightDate
FlightPrice
CurrencyCode

Mark only the booking identifier fields as CDS keys.

Run:

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Ctrl + F2

Activate:

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Ctrl + F3

Preview:

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F8

Part 6 — Define `_Customer`

Create an association to:

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/DMO/I_CUSTOMER

Use the name:

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_Customer

Choose the cardinality based on:

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one booking → how many customer targets?

Use:

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$projection.CustomerId

in the ON condition.

Hint

The target key is named:

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CustomerID

Part 7 — Add Customer path fields

Through _Customer, expose:

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CustomerFirstName
CustomerLastName

The target fields are:

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FirstName
LastName

Use CDS path expressions.

Part 8 — Expose `_Customer`

Add:

abap

_Customer

itself to the element list.

Activate.

Open Data Preview.

Use:

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Follow Association
  → _Customer

Confirm that ADT navigates to the related customer data.

Part 9 — Define `_Carrier`

Create an association to:

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/DMO/I_CARRIER

Use:

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_Carrier

Use the current projection's:

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CarrierId

in the relationship condition.

Expose the target's:

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Name

as:

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CarrierName

Then expose:

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_Carrier

itself.

Part 10 — Follow `_Carrier`

Activate.

Open Data Preview.

Choose:

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Follow Association
  → _Carrier

Verify target fields such as:

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AirlineID
Name
CurrencyCode

against the booking's CarrierId.

Part 11 — Define `_Connection`

This is the key reasoning task.

Target:

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/DMO/I_CONNECTION

Association name:

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_Connection

Before writing the ON condition, answer:

What is the complete target key?

The booking provides:

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CarrierId
ConnectionId

Your association must use the complete relationship.

WARNING

Do not associate only on ConnectionId.

/DMO/I_CONNECTION has a composite key.

Hint

Your condition needs two comparisons joined with:

abap

and

Part 12 — Add Connection path fields

Through _Connection, expose:

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DepartureAirportId
DestinationAirportId
DepartureTime
ArrivalTime

The target provides:

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DepartureAirport
DestinationAirport
DepartureTime
ArrivalTime

Part 13 — Expose `_Connection`

Add:

abap

_Connection

to the element list.

Activate.

Open Data Preview and use:

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Follow Association
  → _Connection

Check that the target:

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AirlineID
ConnectionID

matches:

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CarrierId
ConnectionId

from the booking.

Part 14 — Final scalar model requirements

Your CDS entity should expose:

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TravelId
BookingId
BookingDate

CustomerId
CustomerFirstName
CustomerLastName

CarrierId
CarrierName

ConnectionId
DepartureAirportId
DestinationAirportId
DepartureTime
ArrivalTime

FlightDate
FlightPrice
CurrencyCode

It should also expose:

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_Customer
_Carrier
_Connection

Part 15 — Compare the Lesson 4 and Lesson 5 designs

Write:

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Lesson 4:
Booking __________ Customer

Lesson 5:
Booking __________ Customer

Use:

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JOIN
ASSOCIATION

Then answer:

What capability does the exposed association provide that a copied CustomerName scalar field alone does not?

Part 16 — SQL Console

Query:

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ZI_BOOKING_ASSOC_###

Return at least:

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TravelId
BookingId
CustomerFirstName
CustomerLastName
CarrierName
DepartureAirportId
DestinationAirportId
FlightDate

Order by:

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TravelId
BookingId

The SQL query should not contain joins to Customer, Carrier, or Connection.

Part 17 — Filter by Carrier

Choose a CarrierId present in your booking data.

Filter in SQL Console.

Confirm that:

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CarrierName

is available even though it came through an association path.

Part 18 — Create the Reader

Create:

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ZCL_BOOKING_ASSOC_READER_###

Do not implement:

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IF_OO_ADT_CLASSRUN

Define:

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TT_BOOKINGS

as a standard table of:

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ZI_BOOKING_ASSOC_###

with:

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WITH EMPTY KEY

Part 19 — Implement `GET_ALL`

Create:

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GET_ALL

Requirements:

return TT_BOOKINGS;
select from ZI_BOOKING_ASSOC_###;
use FIELDS *;
order by TravelId, BookingId;
contain no explicit joins;
contain no association definitions.

Part 20 — Implement `GET_BY_CARRIER`

Create:

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GET_BY_CARRIER

Import:

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carrier_id

Requirements:

select from ZI_BOOKING_ASSOC_###;
filter on CarrierId;
use an ABAP SQL host variable;
return TT_BOOKINGS;
order by the booking key.

Part 21 — Create the Runner

Create:

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ZCL_CDS_L05_PRACTICE_###

Implement:

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IF_OO_ADT_CLASSRUN

In main:

instantiate the Reader;
call GET_ALL;
loop through the result;
display a useful line containing:

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TravelId/BookingId
FirstName LastName
CarrierName
DepartureAirportId → DestinationAirportId

Design the exact format yourself.

Part 22 — Test `GET_BY_CARRIER`

Use a carrier ID present in your tenant.

Call:

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GET_BY_CARRIER

Display the result.

Confirm the architecture:

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Runner
  ↓
Reader
  ↓
ZI_BOOKING_ASSOC_###
  ↓
associations

The Reader and Runner should not recreate the relationships.

Part 23 — Cardinality table

Complete:

Association	Cardinality	Why?
`_Customer`
`_Carrier`
`_Connection`

Your reason must answer:

How many target records are expected for one booking?

Part 24 — Explain a path expression

For:

abap

_Carrier.Name

answer:

What is `_Carrier`?

What is `Name`?

What scalar element did you create from this path?

What database join behavior is generated by default for a CDS path target field?

Part 25 — Scalar field vs exposed association

Explain the difference between:

abap

_Carrier.Name as CarrierName

and:

abap

_Carrier

Use:

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scalar value
relationship
navigation

in your explanation.

Part 26 — Direction

Your model contains:

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Booking → Customer

Does that automatically add:

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Customer → Booking

Explain why or why not.

Part 27 — Optional challenge: `Carrier → Connections`

Create:

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ZI_CARRIER_CONNECTIONS_###

Primary source:

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/DMO/I_CARRIER

Alias:

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Carrier

Expose:

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CarrierId
CarrierName

Create an association:

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_Connections

to:

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/DMO/I_CONNECTION

Decide cardinality based on:

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one carrier → how many connections?

Expose the association itself.

Do not flatten every connection field into the carrier row.

Part 28 — Follow the to-many association

Activate:

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ZI_CARRIER_CONNECTIONS_###

Open Data Preview.

Use:

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Follow Association
  → _Connections

Inspect the related connection records.

Answer:

Why is `_Connections` not `[1..1]`?

Why can one source carrier lead to several target rows?

Part 29 — Connect to Lesson 4 row multiplication

Answer:

If you flatten a target field through a to-many association, why can one source row become several result rows?

Use the Lesson 4 concept:

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row multiplication

Part 30 — Reasoning questions

Answer in your own words.

1. What does a CDS association represent?

2. How is an association different from an explicit join?

3. Why are associations directional?

4. What does cardinality describe?

5. Why is `_Connection` a to-one relationship from Booking?

6. Why must `_Connection` use both `CarrierId` and `ConnectionId`?

7. What does `$projection.CustomerId` mean?

8. What does `_Customer.LastName` mean?

9. What happens when a path target field is used in a CDS element list?

10. What does exposing `_Customer` add to the public CDS model?

11. What ADT feature lets you inspect an exposed association?

12. Why can `Carrier → Connections` be `[0..*]` while `Booking → Carrier` is `[1..1]`?

13. Why is cardinality more than documentation?

Submission checklist

Useful ADT shortcuts

Action	Shortcut
Open ABAP Development Object	`Ctrl + Shift + A`
Code completion	`Ctrl + Space`
Navigate	`F3` / `Ctrl + click` where supported
Syntax check	`Ctrl + F2`
Activate current object	`Ctrl + F3`
Activate inactive objects	`Ctrl + Shift + F3`
CDS Data Preview	`F8`
Run console class	`F9`
Format source	`Shift + F1`

Lesson 5 Practice — Booking Associations ​

Objects to create ​

Part 1 — Inspect the target CDS entities ​

/DMO/I_CUSTOMER ​

/DMO/I_CARRIER ​

/DMO/I_CONNECTION ​

Part 2 — Inspect /DMO/BOOKING ​

Part 3 — Plan the relationships ​

Part 4 — Create ZI_BOOKING_ASSOC_### ​

Part 5 — Build the base model first ​

Part 6 — Define _Customer ​

Part 7 — Add Customer path fields ​

Part 8 — Expose _Customer ​

Part 9 — Define _Carrier ​

Part 10 — Follow _Carrier ​

Part 11 — Define _Connection ​

Part 12 — Add Connection path fields ​

Part 13 — Expose _Connection ​

Part 14 — Final scalar model requirements ​

Part 15 — Compare the Lesson 4 and Lesson 5 designs ​

Part 16 — SQL Console ​

Part 17 — Filter by Carrier ​

Part 18 — Create the Reader ​

Part 19 — Implement GET_ALL ​

Part 20 — Implement GET_BY_CARRIER ​

Part 21 — Create the Runner ​

Part 22 — Test GET_BY_CARRIER ​

Part 23 — Cardinality table ​

Part 24 — Explain a path expression ​

What is _Carrier? ​

What is Name? ​

What scalar element did you create from this path? ​

What database join behavior is generated by default for a CDS path target field? ​

Part 25 — Scalar field vs exposed association ​

Part 26 — Direction ​

Part 27 — Optional challenge: Carrier → Connections ​

Part 28 — Follow the to-many association ​

Why is _Connections not [1..1]? ​

Why can one source carrier lead to several target rows? ​

Part 29 — Connect to Lesson 4 row multiplication ​

Part 30 — Reasoning questions ​

1. What does a CDS association represent? ​

2. How is an association different from an explicit join? ​

3. Why are associations directional? ​

4. What does cardinality describe? ​

5. Why is _Connection a to-one relationship from Booking? ​

6. Why must _Connection use both CarrierId and ConnectionId? ​

7. What does $projection.CustomerId mean? ​

8. What does _Customer.LastName mean? ​

9. What happens when a path target field is used in a CDS element list? ​

10. What does exposing _Customer add to the public CDS model? ​

11. What ADT feature lets you inspect an exposed association? ​

12. Why can Carrier → Connections be [0..*] while Booking → Carrier is [1..1]? ​

13. Why is cardinality more than documentation? ​

14. How do associations prepare a CDS model for later RAP/service navigation? ​

Submission checklist ​

Useful ADT shortcuts ​

Lesson 5 Practice — Booking Associations

Objects to create

Part 1 — Inspect the target CDS entities

`/DMO/I_CUSTOMER`

`/DMO/I_CARRIER`

`/DMO/I_CONNECTION`

Part 2 — Inspect `/DMO/BOOKING`

Part 3 — Plan the relationships

Part 4 — Create `ZI_BOOKING_ASSOC_###`

Part 5 — Build the base model first

Part 6 — Define `_Customer`

Part 7 — Add Customer path fields

Part 8 — Expose `_Customer`

Part 9 — Define `_Carrier`

Part 10 — Follow `_Carrier`

Part 11 — Define `_Connection`

Part 12 — Add Connection path fields

Part 13 — Expose `_Connection`

Part 14 — Final scalar model requirements

Part 15 — Compare the Lesson 4 and Lesson 5 designs

Part 16 — SQL Console

Part 17 — Filter by Carrier

Part 18 — Create the Reader

Part 19 — Implement `GET_ALL`

Part 20 — Implement `GET_BY_CARRIER`

Part 21 — Create the Runner

Part 22 — Test `GET_BY_CARRIER`

Part 23 — Cardinality table

Part 24 — Explain a path expression

What is `_Carrier`?

What is `Name`?

What scalar element did you create from this path?

What database join behavior is generated by default for a CDS path target field?

Part 25 — Scalar field vs exposed association

Part 26 — Direction

Part 27 — Optional challenge: `Carrier → Connections`

Part 28 — Follow the to-many association

Why is `_Connections` not `[1..1]`?

Why can one source carrier lead to several target rows?

Part 29 — Connect to Lesson 4 row multiplication

Part 30 — Reasoning questions

1. What does a CDS association represent?

2. How is an association different from an explicit join?

3. Why are associations directional?

4. What does cardinality describe?

5. Why is `_Connection` a to-one relationship from Booking?

6. Why must `_Connection` use both `CarrierId` and `ConnectionId`?

7. What does `$projection.CustomerId` mean?

8. What does `_Customer.LastName` mean?

9. What happens when a path target field is used in a CDS element list?

10. What does exposing `_Customer` add to the public CDS model?

11. What ADT feature lets you inspect an exposed association?

12. Why can `Carrier → Connections` be `[0..*]` while `Booking → Carrier` is `[1..1]`?

13. Why is cardinality more than documentation?

14. How do associations prepare a CDS model for later RAP/service navigation?

Submission checklist

Useful ADT shortcuts