Add leading zeros only to numeric field in CDS?

Question

In my AS ABAP 7.50 system, I have a table where the material length is 18 and I need to expose it via CDS as if the material length was 40 like in S/4. The material IDs in the system can be numeric (with leading zeros) or alphanumeric. The material field needs to be casted to MATNR40, and if the ID is numeric, the leading zeros need to be added up to the 40 characters.

First, I tried `lpad. But of course, it also adds the leading zeros to the alphanumeric values:

lpad( cast(matnr as matnr40), 40, '0' ) as material_long,

Then I added a case but I'm not able to make the condition work as I expect. As konstantin confirmed in the comments, it's not possible to use regex here as I attempted:

case when matnr like '%[^0-9.]%'
     then lpad( cast(matnr as matnr40), 40, '0' )
     else cast(matnr as matnr40)
end as material_long,

Is there a solution within the CDS itself to this problem?

Source table:

MATNR18	Description
000000000000000142	Numeric ID material
MATERIAL_2	Alphanumeric ID

Expected result:

MATNR40	Description
0000000000000000000000000000000000000142	Numeric ID material
MATERIAL_2	Alphanumeric ID

Answer 1

Due to the limited functionality in CDS syntax the only way I see is to nest 10 REPLACE functions to remove digits and compare the result with initial string. If it is initial, then you have only digits, so you can LPAD them with zeroes. If not - use the original value.

Here's my code:

@AbapCatalog.sqlViewName: 'Z_V_TEST'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: 'Test'
define view Z_TEST as select from /bi0/mmaterial {
    cast(
      case replace(replace(replace(replace(replace(replace(replace(replace(replace(replace(material,
        '0', ''), '1', ''), '2', ''), '3', ''), '4', ''), '5', ''), '6', ''), '7', ''), '8', ''), '9', '')
        when ''
        then lpad(material, 40, '0')
        else material
      end as abap.char(40)
    ) as MATERIAL_ALPHA,
    material
}

And the result is:

REPORT Z_TEST.

    select *
    from Z_V_TEST
    where material in ('LAMP', '000000000000454445')

      into table @data(lt_res)
    .
    cl_demo_output=>display( lt_res ).



MATERIAL_ALPHA                           | MATERIAL 
-----------------------------------------+-------------------
0000000000000000000000000000000000454445 | 000000000000454445 
LAMP                                     | LAMP