CDS View

CDS view是SAP目前推出的下一代database views，SAP认为传统的database view只是将多张表进行关联，CDS View是一个成熟的Data Model，它有很多SE11中所没有的新特性，并且可以被SAP产品外的Application使用。

1 在Eclipse中创建CDS View

右击新建ABAP Object，选择CSD->Data Definition

点击下一步往后，在此页面可以选择模板，其中 ${sql_view_name}是将来在SE11中生成的view的名称

2 CDS View代码

2.1 Define View / Define View with Join

使用模板生成的代码如下

@AbapCatalog.sqlViewName: 'ZV_MONSTERS'
@AbapCatalog.compiler.compareFilter: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: 'Monster CDS views'
define view zcds_monsters as select from ztmonster_header as
monster_header
inner join ztmonster_items as monster_items
    on monster_header.db_key = monster_items.db_key
left outer join ztmonster_pets as monster_pets
    on monster_header.monster_number = monster_pets.owner
{
    key monster_header.monster_number as monster_number ,
    monster_header.name as monster_name ,
    LPAD ( monster_header.tax_number, 10 , '0' ) as hat_size ,
    SUBSTRING ( monster_header.name, 1 , 1 ) as first_initial ,
    case monster_header.evilness
        when 'BANKER_STYLE_EVIL' then 'REALLY SCARY'
        when 'EVIL' then
            case monster_header.strength
                when 'REALLY STRONG ' then 'SCARY'
                else ' NOT SO SCARY REALLY '
                end
        when 'SLIGHTLY_EVIL' then 'SLIGHTLY SCARY '
        else 'NOT REALLY SCARY AT ALL '
    end as scariness
}
where monster_header.sanity < 10
    and monster_header.color = 'GREEN'

以@开头的为注解，除了默认的注解，可以自己添加比如buffer的注解，按F1可以获得注解的介绍

@AbapCatalog.buffering.status : #ACTIVE
@AbapCatalog.buffering.type : #SINGLE

CSD veiw中，可以使用 inner jion / left jion等join命令，相比ABAP定义更广泛了，通过as添加别名，使得看起来更具有实际意义。CDS中访问表的字段使用点号.而不是传统ABAP中的波浪号~。在SE11中我们定义字段时，左边是human-friendly names, 比如CUSTOMER / CUSTOMER_NAME，而右边是 data element ,比如 KUNNR and NAME1，CDS 中只定义human-friendly names，其类型有所取出的数据库表字段类型自动定义。这有点类似于ABAP中通过DATA( )来定义数据的结构。所有的字段都放在{}中，在select jion关键词后，在where关键词前。上面例子中，通过LPAD可以将tax_number的值比如3补全成0000000003，通过SUBSTRING来取首字母。字段定义还可以用case语句。最后跟where条件语句，cds中可以用IS NULL / IS NOT NULL来判断是否为空。
激活后，在se11中可以查看view

2.2 Define View with Association

SAP希望大家更多的是用association而不是jion，这更体现了概念思维，assocation不仅仅是jion，它是数据字典存储的一种可能的jion连接的metadata，实际的jion在association被使用时才创建。
两张表通过外键链接对我们来说很容易理解，但这其实与实际不匹配，比如我们下3个不同类型订单时，我们对header数据和item数据并没有有意思地去区别，因为通常概念中，很明显一个订单要有item数据，否则是没有意义的。再比如通过表LFA1/LFM1寻找supplier的purchasing related data，通过association，我们可以用Supplier.PurchasingData.BlockingFlag 而不是LFM1 ~ SPERM 。当你创建了association view连接起address和customer，就可以在order item的customer中重用这个association view。
Association View定义如下，monster可能没有pets，也可能有多个，因此设为[0..*]，header和item的关系可以设成[1..*]，如果jion两个主键字段，可以用[1..1]。另外，SAP推荐assocation的名字前面加下划线来区分CDS view中标准字段。

@AbapCatalog.sqlViewName: 'zv_monsters_ass'
@AbapCatalog.compiler.compareFilter: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: 'Monsters CDS View with Association'
define view Zcds_Monsters_Association as select from ztmonster_header as monster
association [0..*] to ztmonster_pets as _Pet
    on monster.monster_number = _Pet.owner {
    
    key monster.monster_number as MonsterNumber ,
    key _Pet.pet_number as PetNumber ,
    _Pet.owner as Owner ,
    monster.name as OwnerName ,
    _Pet.pet_name as Name ,
    _Pet.pet_type as Type,
    _Pet.pet_species as Species,
    _Pet // Make association public
}

2.3 Define View with Parameters

前面建立的CDS view，其中where条件是hard-code的，我们希望能通过参数来指定where条件，比如传统ABAP中

SELECT * FROM zv_monster_pars
    WHERE color EQ p_color
    AND sanity IN s_sanity .

可以通过如下代码定义参数，参数后面是其data element。

@AbapCatalog.sqlViewName: 'zv_monsters_pars'
@AbapCatalog.compiler.compareFilter: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: 'Monster CDS View with Parameters'
define view Zcds_Monsters_Parameters
    with parameters p_sanity_low : ZDE_MONSTER_SANITY ,
                    p_sanity_high: ZDE_MONSTER_SANITY ,
                    p_color : ZDE_MONSTER_COLOR
as select from ztmonster_header as monster {
    key monster.monster_number as MonsterNumber,
    monster.name as name ,
    monster.color as color ,
    monster.sanity as sanity ,
    monster.strength as strength
}
  where monster.color = :p_color and
     sanity between :p_sanity_low and :p_sanity_high

在程序中可以通过如下代码来调用

SELECT * FROM zcds_monsters_parameters(
    p_color = @p_color ,
    p_sanity_low = @s_sanity- l ow,
    p_sanity_high = @s_sanity-high )
INTO TABLE @DATA(colorful _mad_monster_tablel)
WHERE strength~ 'REALLY_STRONG '.

2.4 Extend View

在SE11中，我们通过append对table或view进行增强，在CDSview中，对原有的CDS View进行增强可以如下

@AbapCatalog.sqlViewAppendName: 'ZV_MONSTERS_EXT'
@EndUserText.label: 'Monster CDS view extension'
extend view ZCDS_MONSTERS with ZCDS_MONSTERS_EXTENSION {
    monster_header.age,
    monster_header.monster_count as counts
}

增强后，原CDS View将有增强标记

在原始view中，可以看到append的字段

2.5 Table Function

定义table function如下，table function必须将clinet作为参数传入，returns中的字段即为返回的字段，取数逻辑放在AMDP Class的方法中。

@EndUserText.label: 'Table Function'
define table function ZCDS_tablefun
with parameters @Environment.systemField: #CLIENT
                clnt : abap.clnt
returns {
  client : s_mandt;
  carrname : s_carrname;
  connid : s_conn_id;
  city_from : s_from_cit;
  city_to : s_to_city;
}
implemented by method ZLL_DEMO_AMDP_FUNCTIONS=>GET_flights;

定义AMDP class，继承接口if_amdp_marker_hdb，

CLASS zll_demo_amdp_functions DEFINITION
  PUBLIC
  FINAL
  CREATE PUBLIC .

  PUBLIC SECTION.

    INTERFACES if_amdp_marker_hdb .
    CLASS-METHODS get_flights FOR TABLE FUNCTION zcds_tablefun .

  PROTECTED SECTION.
  PRIVATE SECTION.

ENDCLASS.


CLASS zll_demo_amdp_functions IMPLEMENTATION.

  METHOD get_flights
         BY DATABASE FUNCTION FOR HDB
         LANGUAGE SQLSCRIPT
         OPTIONS READ-ONLY
         USING scarr spfli.
    RETURN SELECT sc.mandt as client, sc.carrname, sp.connid, sp.cityfrom, sp.cityto
                  from scarr as sc
                    inner join spfli as sp on sc.mandt = sp.mandt and
                                              sc.carrid = sp.carrid
                    ORDER BY sc.carrname, sp.connid;

  endmethod.
ENDCLASS.

2.6 Authority Checks

在DDL中，我们配置@AccessControl.authorizationCheck: #CHECK，一个完整的CDS View需要 DDL + DCL

选择模板，代码如下

@EndUserText.label: 'Authority Check for CDS view' 
@MappingRole: true 
define role Zdcl_Monsters_Parameters { 
    grant 
        select 
            on 
                Zcds_Monsters_Parameters 
                    where 
                      //  condition; 
                      // -- Example WHERE condition 
                      // -- Two-field mapping to PFCG authorization with filter on read authorization
                       ( color ) = aspect pfcg_auth( z_mon_col, color, ACTVT = '03' ) ;
                      // and 
                      // -- Equals-or-initial operator 
                      // ( CustomerCountry ) ?= aspect pfcg_auth( S_ACM_DEMO, SACMCNTRY ) 
                      // or 
                      // -- Reference to the logged on users name 
                      // CreatedBy = aspect User 
                      // or 
                      // -- Literal condition 
                      // isPublic = 'X'; 
 
}