Part#3. CDS View with Expressions and Session Variables

[kumarsanjeev]

This is the 3rd blog post on the CDS detailed explanations after the Introduction post. Refer to the Introduction and blog post indexes here:
https://blogs.sap.com/2019/10/21/part1.-sap-cds-views-demystification/

As you saw in the previous blog post, in the Basic CDS view the data has been read with a simple ‘Select’ statement. So how about some business logic calculations? Can we have some Mathematical Expressions configured in the CDS view?  Yes, absolutely, let’s create a simple CDS view with an Expression to calculate the available seats in business class from table SFLIGHT;



Check the output below.  Column Seats_Avlbl is the result of a mathematical expression configured within CDS view.



 

=> 'WHERE' CLAUSE AND SESSION VARIABLES:

Let's check how to add a 'WHERE' clause to filter the data and how to make use of 'Session Variables'.  Similar to ABAP session variables like sy-datum for current Date, sy-uzeit for current Time etc. , CDS views editor also has session variables which can provide these values.  See below the syntax for Client, system_date, system_language, user can be determined within 'WHERE ' clause.

 



Select 'system_date' to compare 'Current Date' with Flight Date.

@AbapCatalog.sqlViewName: 'ZSQL_VIEW_EXPRSN'

@AbapCatalog.compiler.compareFilter: true

@AbapCatalog.preserveKey: true

@AccessControl.authorizationCheck: #CHECK

@EndUserText.label: 'CDS view with  Expression'

define view ZCDS_VIEW_EXPRESSION as select from sflight 

 {

    key carrid, 

    connid,

    seatsmax_b,

    seatsocc_b,

    fldate,

    (seatsmax_b - seatsocc_b) as Seats_Avlbl

    }

    

 

where fldate <= $session.system_date 

 

In summary, we saw how to add Expressions, Where Clause to the CDS view and how to use Session variables to get some system data.

 

Part# 4. Consume CDS View in an ABAP Program: Check the new ABAP syntax to consume CDS view.

 

Follow for upcoming blog posts: kumarsanjeev

Keep learning..

SK