SAP Hana CDS 开发简介
一、CDS简介
为了利用SAP HANA进行应用程序开发，SAP引入了一个新的基础数据建模，称为核心数据服务（CDS）。使用CDS，数据模型是在数据库服务器上定义和使用的，而不是在应用程序服务器上。CDS还提供了超越传统数据建模工具的功能，包括对概念建模和关系定义、内置函数和扩展的支持。
最初，CDS仅在SAP HANA的设计时和运行时环境中可用。现在，CDS概念在SAP NetWeaver中为ABAP也得到了充分的实现，使开发人员能够在将代码执行下推到数据库的同时，使用ABAP开发工具在ABAP层工作。
CDS简化和统一了定义和使用数据模型的方式，不管你用的是哪种消费技术。从技术上讲，它是对SQL的增强，为您提供了一种数据定义语言(DDL)，用于定义语义丰富的数据库表/视图(CDS实体)和数据库中的用户定义类型。
包括:
- 用于数据模型中的计算和查询的表达式
- 概念层次上的关联，在查询中使用简单的路径表达式代替连接
- 使用附加的(domain specific特殊域)元数据来丰富数据模型的注解。[元数据是“描述数据的数据”。元数据可以为数据说明其元素或属性（名称、大小、数据类型等），或结构（长度、字段、数据列），或其相关数据（位于何处、如何联系、拥有者）。]
CDS版本变更历史：
二、CDS VIEW 创建模板
1、定义单数据源的简单视图
模板：
/*
template 1: Define View
Defines a simple CDS view with one data source.
*/
@AbapCatalog.sqlViewName: '${sql_view_name}'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: '${ddl_source_description}'
define view ${ddl_source_name_editable} as select from ${data_source_name} {
${
cursor}
}
实例（CDS标准写法）：
@AbapCatalog.sqlViewName: 'YV_DEMO01_SCARR'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: 'CDS_DEMO01_SCARR'
define view YCDS_DEMO01_SCARR as
select from scarr
{
--key mandt, -- CDS会自动添加
key carrid,
carrname,
url
};
或者（传统SQL写法）：
@AbapCatalog.sqlViewName: 'YV_DEMO01_SCARR'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: 'CDS_DEMO01_SCARR'
define view YCDS_DEMO01_SCARR as
select
--key mandt, -- CDS会自动添加
key carrid,
carrname,
url
from scarr;
ABAP程序调用（Open SQL）：
REPORT yz_cds_demo.
SELECT *
FROM ycds_demo01_scarr
INTO TABLE @DATA(itab).
cl_demo_output=>display( itab ).
ABAP程序调用（SALV IDA）：
REPORT YZ_IDA_DEMO.
CL_SALV_GUI_TABLE_IDA=>CREATE_FOR_CDS_VIEW( iv_cds_view_name = 'YCDS_DEMO01_SCARR' )->FULLSCREEN( )->DISPLAY( ).
实例（定义字段别名）：
@AbapCatalog.sqlViewName: 'YV_DEMO01_SCARR2'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: 'CDS_DEMO01_SCARR2'
define view YCDS_DEMO02_SCARR
(id, name, url) --field alias
as
select from scarr
{
--key mandt,
key carrid as id, --alias
carrname,
url
};
2、定义两个数据源的JOIN视图
模板：
/*
template 2: Define View with Join
Defines a CDS view which combines two data sources using a left outer join.
The join conditions are specified in the on clause.
*/
@AbapCatalog.sqlViewName: '${sql_view_name}'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: '${ddl_source_description}'
define view ${ddl_source_name_editable} as select from ${data_source_name}
left outer join ${joined_data_source_name}
on ${data_source_name}.${element_name} = ${joined_data_source_name}.${joined_element_name} {
${
cursor}
}
实例：
@AbapCatalog.sqlViewName: 'YV_DEMO02_JOIN'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: 'CDS_DEMO02_JOIN'
define view YCDS_DEMO02_JOIN as
select from spfli
left outer join scarr
on scarr.carrid = spfli.carrid
{
key spfli.carrid,
key spfli.connid,
scarr.carrname
};
ABAP调用程序：
REPORT yz_cds_demo.
SELECT *
FROM ycds_demo02_join
INTO TABLE @DATA(itab).
cl_demo_output=>display( itab ).
3、定义具有关联关系的视图
模板：
/*
template 3: Define View with Association
Defines a CDS view with a public association to another data source.
The association can be used in the select list as well as by other CDS views which use this CDS view as a data source.
*/
@AbapCatalog.sqlViewName: '${sql_view_name}'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: '${ddl_source_description}'
define view ${ddl_source_name_editable} as select from ${data_source_name}
association [${
1}] to ${target_data_source_name} as ${_association_name}
on $$projection.${element_name} = ${_association_name}.${target_element_name} {
${
cursor}
${_association_name} // Make association public
}
实例：
@AbapCatalog.sqlViewName: 'YV_DEMO03_ASSOCI'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: 'CDS_DEMO03_ASSOCIATION'
define view YCDS_DEMO03_ASSOCIATION as
select from spfli
association to scarr as _scarr
on $projection.carrid = _scarr.carrid
{
key spfli.carrid,
key spfli.connid,
--_scarr.carrname,
_scarr // Make association public, joined on demand
}
在HanaStudio中预览数据：
HANA访问数据：
select * from YV_DEMO03_ASSOCI; -- 未访问关联
ABAP访问数据：
REPORT yz_cds_demo.
PARAMETERS: p_carrid TYPE scarr-carrid.
SELECT carrid, connid, \_scarr-carrname AS flightname "访问关联
FROM YCDS_DEMO03_ASSOCIATION
where carrid = @p_carrid
INTO TABLE @DATA(itab).
cl_demo_output=>display( itab ).
4、定义父类关联关系的视图
模板：
/*
template 4: Define View with To-Parent Association
Defines a CDS view with a specialized association to its parent CDS entity.
Compositions and to-parent associations are used to define the structure of a business object which can be used in the ABAP RESTful Programming Model.
*/
@AbapCatalog.sqlViewName: '${sql_view_name}'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: '${ddl_source_description}'
define view ${ddl_source_name_editable} as select from ${data_source_name}
association to parent ${target_data_source_name} as ${_association_name}
on $$projection.${element_name} = ${_association_name}.${target_element_name} {
${
cursor}
${_association_name} // Make association public
}
实例：
@AbapCatalog.sqlViewName: 'YV_DEMO04_TOPARE'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: 'CDS_DEMO04_TOPARENT'
define view YCDS_DEMO04_TOPARENT as
select from spfli
association to parent YCDS_DEMO01_SCARR as _scarr
on $projection.carrid = _scarr.id {
key spfli.carrid,
key spfli.connid,
_scarr.id, // Make association public
_scarr
}
5、定义单个入参的视图
模板：
/*
template 5: Define View with Parameters
Defines a CDS view with a single input parameter.
The input parameter can be used as an element in the select list
or as an operand in conditional or arithmetic expressions.
*/
@AbapCatalog.sqlViewName: '${sql_view_name}'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: '${ddl_source_description}'
define view ${ddl_source_name_editable}
with parameters ${parameter_name} : ${parameter_type}
as select from ${data_source_name} {
${
cursor}
}
实例：
@AbapCatalog.sqlViewName: 'YV_DEMO05_PARAM'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: 'CDS_DEMO05_PARAMETERS'
define view YCDS_DEMO05_PARAMETERS
with parameters p_carrid : s_carr_id
as select from spfli {
key connid,
cityfrom,
cityto
}
where carrid = $parameters.p_carrid;
SE11图（不支持查看表数据）：
SE16N图（可以执行，需要输入参数）：
ABAP程序调用：
REPORT yz_cds_demo.
PARAMETERS: p_carrid TYPE scarr-carrid.
SELECT *
FROM ycds_demo05_parameters( p_carrid = @p_carrid )
INTO TABLE @DATA(itab).
cl_demo_output=>display( itab ).
HANA 查询数据：
select * from YV_DEMO05_PARAM('AA') where mandt = 200;
--或者
select * from YV_DEMO05_PARAM( p_carrid => 'AA' ) where mandt = 200;
6、定义简单的投影视图实体
模板：用于屏蔽一些字段(一般用于保护数据时使用)。
/*
template 6: Define Projection View
Defines a simple CDS projection view.
*/
@EndUserText.label: '${ddl_source_description}'
@AccessControl.authorizationCheck: #CHECK
define view entity ${ddl_source_name_editable} as projection on ${data_source_name} {
${
cursor}
}
实例：
@EndUserText.label: 'CDS_DEMO06_PROJECTION'
@AccessControl.authorizationCheck: #NOT_REQUIRED
define view entity YCDS_DEMO06_PROJECTION
as projection on YCDS_DEMO04_TOPARENT {
key carrid,
key connid
}
7、定义继承的视图
/*
template 7: Extend View
Extends an existing CDS view by adding the specified elements
to the select list of the CDS view using a view enhancement.
*/
@AbapCatalog.sqlViewAppendName: '${sql_view_append_name}'
@EndUserText.label: '${ddl_source_description}'
extend view ${view_name} with ${ddl_source_name_editable} {
${data_source_name}.${element_name}
}
实例：
@AbapCatalog.sqlViewAppendName: 'YV_DEMO07_EXTEND'
@EndUserText.label: 'CDS_DEMO07_EXTEND'
extend view YCDS_DEMO02_JOIN //原CDS，有三个字段
with YCDS_DEMO07_EXTEND //新CDS，追加一个字段
{
scarr.currcode
}
8、定义带有入参的表函数
模板：AMDP FUNCTION实现。
/*
template 8: Define Table Function with Parameters
Defines the type signature of a client dependent CDS table function with importing parameters.
The CDS table function is implemented in the specified ABAP method.
The CDS table function can be used in Open SQL and as a data source
in other CDS view definitions.
*/
@EndUserText.label: '${ddl_source_description}'
define table function ${ddl_source_name_editable}
with parameters ${parameter_name} : ${parameter_type}
returns {
${client_element_name} : abap.clnt;
${element_name} : ${element_type};
${
cursor}
}
implemented by method ${class_name}=>${method_name};
实例：
@EndUserText.label: 'ADMP_DEMO_SCARR'
define table function YCDS_ADMP_DEMO_SCARR
with parameters
@Environment.systemField: #CLIENT
p_clnt : abap.clnt
returns {
mandt : abap.clnt;
carrid : s_carr_id;
carrname : s_carrname;
url : s_carrurl;
}
implemented by method ycl_amdp_hdb_demo=>get_scarr_for_cds;
具体参考：X档案：SAP ABAP 中 AMDP 简介及实现方法
9、定义带有入参的抽象实体
模板：仅描述类型属性且未实例化任何数据库对象的 CDS 实体。
/*
template 9: Define Abastract Entity with Parameters
Defines an abstract CDS entity with a single input parameter.
*/
@EndUserText.label: '${ddl_source_description}'
define abstract entity ${ddl_source_name_editable}
with parameters ${parameter_name} : ${parameter_type} {
${element_name} : ${element_type};
${
cursor}
}
实例：
@EndUserText.label: 'CDS_DEMO09_ABSTRACT'
define abstract entity YCDS_DEMO09_ABSTRACT
with parameters p_carrid : s_carr_id
{
connid : s_conn_id;
cityfrom : s_from_cit;
cityto : s_to_city;
}
10、定义父子层次视图
模板：
/*
template 10: Define Parent Child Hierarchy
Defines a simple CDS parent child hierarchy.
*/
define hierarchy ${ddl_source_name_editable}
as parent child hierarchy (
source ${data_source_name}
child to parent association ${_association_name}
start where ${element_name} = ${
value}
siblings order by ${order_by_element_name}
)
{
${element_name}
${
cursor}
}
定义父子层次表：YTB_DEMO_HIER
插入数据：
CREATE COLUMN TABLE "SAPHANADB"."YTB_DEMO_HIER"
(
"MANDT" NVARCHAR(3) DEFAULT '000' NOT NULL ,
"ID" INTEGER CS_INT DEFAULT 0 NOT NULL ,
"PID" INTEGER CS_INT DEFAULT 0 NOT NULL ,
"NAME" NVARCHAR(20) DEFAULT '' NOT NULL ,
CONSTRAINT "YTB_DEMO_HIER~0" PRIMARY KEY ("MANDT","ID")
);
insert into YTB_DEMO_HIER values('200', 1, 0, '图书');
insert into YTB_DEMO_HIER values('200', 2, 1, '教材类');
insert into YTB_DEMO_HIER values('200', 3, 1, '计算机类');
insert into YTB_DEMO_HIER values('200', 4, 3, 'Java');
insert into YTB_DEMO_HIER values('200', 5, 3, '.Net');
insert into YTB_DEMO_HIER values('200', 6, 3, 'SAP');
insert into YTB_DEMO_HIER values('200', 7, 1, '文学类');
insert into YTB_DEMO_HIER values('200', 8, 1, '科幻类');
insert into YTB_DEMO_HIER values('200', 9, 8, '三体');
insert into YTB_DEMO_HIER values('200', 10, 8, '流浪地球');
定义父子层次数据源：CDS View
@AbapCatalog.sqlViewName: 'YTB_DEMO_HIER_S'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: 'CDS_DEMO10_HIERARCHY_SOURCE'
define view YCDS_DEMO10_HIERARCHY_SOURCE
as select from ytb_demo_hier
association[1..1] to YCDS_DEMO10_HIERARCHY_SOURCE as _tree
on $projection.parent= _tree.id
{
_tree,
key id,
pid as parent,
name
}
或者：CDS View 实体
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: 'CDS_DEMO10_HIERARCHY_VIEW'
define view entity YCDS_DEMO10_HIERARCHY_VIEW
as select from ytb_demo_hier
association[1..1] to YCDS_DEMO10_HIERARCHY_VIEW as _tree
on $projection.parent= _tree.id
{
_tree,
key id,
pid as parent,
name
}
定义父子层次关系视图：
define hierarchy YCDS_DEMO10_HIERARCHY
with parameters
p_id : abap.int4
as parent child hierarchy (
source
--YCDS_DEMO10_HIERARCHY_SOURCE --两者都可以
YCDS_DEMO10_HIERARCHY_VIEW --两者都可以
child to parent association _tree
start where
id = :p_id
siblings order by
id ascending
)
{
id,
parent,
name
}
在Hana中预览数据：
在Hana SQL中查询数据：
select * from YTB_DEMO_HIER_S; --sql view，可以访问，有数据
select * from YCDS_DEMO10_HIERARCHY_SOURCE; --cds view，无法访问
select * from YCDS_DEMO10_HIERARCHY_VIEW; --cds view entity，可以访问，没有数据
select * from YCDS_DEMO10_HIERARCHY( p_id => 3 ); --可以访问，没有数据
在ABAP中访问：
REPORT YZ_CDS_DEMO.
PARAMETERS: p_id type YCDS_DEMO10_HIERARCHY_VIEW-id.
SELECT FROM YCDS_DEMO10_HIERARCHY( p_id = @p_id )
FIELDS id,
parent,
name,
hierarchy_rank,
hierarchy_tree_size,
hierarchy_parent_rank,
hierarchy_level,
hierarchy_is_cycle,
hierarchy_is_orphan,
node_id,
parent_id
INTO TABLE @DATA( cds_result ).
cl_demo_output=>display( cds_result ).
11、定义单个入参的客户实体
模板：
/*
template 11: Define Custom Entity with Parameters
Defines a custom CDS entity with a single input parameter.
*/
@EndUserText.label: '${ddl_source_description}'
define custom entity ${ddl_source_name_editable}
with parameters ${parameter_name} : ${parameter_type} {
key ${key_element_name} : ${key_element_type};
${element_name} : ${element_type};
${
cursor}
}
实例：
（1）定义CDS客户实体：YCDS_DEMO11_CUSTOM_ENTITY
@ObjectModel.query.implementedBy : 'ABAP:YCL_CUSTOM_ENTITY'
@EndUserText.label: 'CDS_DEMO11_CUSTOM_ENTITY'
define custom entity YCDS_DEMO11_CUSTOM_ENTITY
with parameters p_id : abap.char(3)
{
key carrid : abap.char(3); // Returning fields are mentioned between {} just like ordinary CDS
carrname : abap.char(20); // Returning field set must contain a key or key combination
url : abap.char(255);
}
（2）定义ABAP实现类：YCL_CUSTOM_ENTITY
class YCL_CUSTOM_ENTITY definition
public
final
create public .
public section.
interfaces IF_RAP_QUERY_PROVIDER .
protected section.
private section.
ENDCLASS.
CLASS YCL_CUSTOM_ENTITY IMPLEMENTATION.
* <SIGNATURE>---------------------------------------------------------------------------------------+
* | Instance Public Method YCL_CUSTOM_ENTITY->IF_RAP_QUERY_PROVIDER~SELECT
* +-------------------------------------------------------------------------------------------------+
* | [--->] IO_REQUEST TYPE REF TO IF_RAP_QUERY_REQUEST
* | [--->] IO_RESPONSE TYPE REF TO IF_RAP_QUERY_RESPONSE
* | [!CX!] CX_RAP_QUERY_PROV_NOT_IMPL
* | [!CX!] CX_RAP_QUERY_PROVIDER
* +--------------------------------------------------------------------------------------</SIGNATURE>
method IF_RAP_QUERY_PROVIDER~SELECT.
data:IT_RESULT type table of YCDS_DEMO11_CUSTOM_ENTITY. "Internal table to be returned , easier to handle return if internal table is as same type of our data definition
data: LV_PARAM type STRING."Local variable to fetch and save parameter value
try.
try.
if IO_REQUEST->IS_DATA_REQUESTED( ). "Fetching incoming data
IO_REQUEST->GET_PAGING( ).
data(LT_FILTER_COND) = IO_REQUEST->GET_PARAMETERS( ). "Setting the filter condition, fetching parameter names from data definition
LV_PARAM = value #( LT_FILTER_COND[ PARAMETER_NAME = 'p_id' ]-VALUE optional ). "Fetching the parameter value
"Using the parameter we could do whatever we want , like selecting from a table , doing certain calculations etc
select * from scarr where carrID = @LV_PARAM into CORRESPONDING FIELDS OF TABLE @IT_RESULT.
IO_RESPONSE->SET_TOTAL_NUMBER_OF_RECORDS( LINES( IT_RESULT ) ). "setting the total number of records which will be sent
IO_RESPONSE->SET_DATA( IT_RESULT ). "returning the data as internal table
endif.
catch CX_RAP_QUERY_PROVIDER into data(LX_EXC). "CX_A4C_RAP_QUERY_PROVIDER is now deprecated so use CX_RAP_QUERY_PROVIDER
endtry.
catch CX_RFC_DEST_PROVIDER_ERROR into data(LX_DEST).
endtry.
endmethod.
ENDCLASS.
（3）定义服务：
@EndUserText.label: 'SVS_EXPOSE_CUSTOM_ENTITY'
define service YSVS_EXPOSE_CUSTOM_ENTITY {
expose YCDS_DEMO11_CUSTOM_ENTITY;
}
（4）服务如何使用（暂时还没研究到）
三、CDS VIEW ENTITY 创建模板
说明：
NW 7.55 以上引入。
CDS View Entity 对象，可以在ABAP中访问，但是不能在Hana Sql中访问（无数据）。
12、定义单数据源的简单视图实体
模板：
/*
template 12: Defines a simple CDS view entity with one data source.
*/
@AbapCatalog.viewEnhancementCategory: [#NONE]
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: '${ddl_source_description}'
@Metadata.ignorePropagatedAnnotations: true
@ObjectModel.usageType:{
serviceQuality: #X,
sizeCategory: #S,
dataClass: #MIXED
}
define view entity ${ddl_source_name_editable} as select from ${data_source_name}
{
${data_source_elements}${
cursor}
}
实例：
@AbapCatalog.viewEnhancementCategory: [#NONE]
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: 'CDS_DEMO12_VIEW_ENTITY'
@Metadata.ignorePropagatedAnnotations: true
@ObjectModel.usageType:{
serviceQuality: #X,
sizeCategory: #S,
dataClass: #MIXED
}
define view entity YCDS_DEMO12_VIEW_ENTITY as select from scarr
{
key carrid,
carrname,
url
}
13、定义根视图实体
模板：
/*
template 13: Defines a root CDS view entity with a specialized association to a child CDS entity.
Root nodes, compositions and to-parent associations are used to define the structure of a business object which can be used in the ABAP RESTful programming model.
*/
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: '${ddl_source_description}'
define root view entity ${ddl_source_name_editable} as select from ${data_source_name}
composition of ${target_data_source_name} as ${_association_name}
{
${data_source_elements}${
cursor}
${_association_name} // Make association public
}
14、定义关联父实体的视图实体
模板：
/*
template 14: Defines a CDS view entity with a specialized association to its parent CDS entity.
Compositions and to-parent associations are used to define the structure of a business object which can be used in the ABAP RESTful programming model.
*/
@AccessControl.authorizationCheck: #NOT_REQUIRED
@EndUserText.label: '${ddl_source_description}'
define view entity ${ddl_source_name_editable} as select from ${data_source_name}
association to parent ${target_data_source_name} as ${_association_name}
on $$projection.${element_name} = ${_association_name}.${target_element_name}
{
${data_source_elements}${
cursor}
${_association_name} // Make association public
}
15、继承投影视图实体
模板：
/*
template 15: Extends an existing CDS projection view entity by adding the specified elements to its select list.
*/
extend view entity ${view_name} with {
${base_data_source_name}.${element_name}
}
16、继承抽象实体
模板：
/*
template 16: Extends an abstract CDS entity by adding the specified elements to its select list.
*/
extend abstract entity ${entity_name} with
{
${element_name} : ${element_type};
}
17、继承客户实体
模板：
/*
template 17: Extends a custom CDS entity by adding the specified elements to its select list.
*/
extend custom entity ${entity_name} with
{
${element_name} : ${element_type};
}
created by xlevon on 20230206.
原创文章，转载请注明来源-X档案
参考文档：
ABAP CDS - Syntax
Working with Hierarchies in ABAP SQL
Custom Entities – Business Technology Platform (SAP Cloud Platform)