ABAP CDS - SELECT

SELECT [DISTINCT] { select_list
                    FROM data_source
                    [association1 association2 ...] }
                | { FROM data_source
                    [association1 association2 ...]
                    {select_list} }
                  [clauses]
Effect
The SELECT statement defines a query performed on the data sources specified in data_source for a CDS view in ABAP CDS. Possible data sources are database tables defined in ABAP Dictionary, classic views, or other CDS views.

• select_list defines the components read in a list.

• association1, association2, ... define associations for the current SELECT statement. These associations can be accessed in data_source and in select_list using path expressions.

• DISTINCT removes duplicates from the results list.

Both forms of the code have the same semantics. The curly brackets around select_list in the second variant is part of the syntax.
The optional additions clauses are SELECT clauses that enable conditions, groupings and union sets to be specified or created.
Example
The CDS view business_partner_role defined here is a view of an existing CDS view, business_partner. An element bp_role is defined in the SELECT list and given the comment Business partner role. Any duplicate values of the element are removed using DISTINCT.

@AbapCatalog.sqlViewName: 'BPA_ROLE_VW'
define view business_partner_role as
  select distinct
         from business_partner
         { business_partner.role //Business partner role
         }

The CDS view business_partner_role can be addressed in ABAP programs using Open SQL, for example:

SELECT * FROM business_partner_role INTO TABLE tab ...

The addition of DISTINCT of SELECT is no longer needed in this case. 

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