Use of $Projection Keyword and Filters in Association

[former_member191728]

Hi Experts,

I want to know the use of $projection  keyword. when should we use this keyword.

I want to know the difference of below two statements

business_partners[ bp_role = '01' ].company_name as customer_name --

I know this statement is used to display the customer name whose Bp_role value is equal to 01

But I didn't understand the below statement

mard[1: matnr = '0000000010'].lgort

Can you also please tell me about use of associations. Since we can use inner joins in which business scenario we can use associations.

Thanks

Pawan Akella

[thomasgauweiler]

Hi Pawin,

$projection is used, when you want to refer to a name defined as alias in the projection list e.g. in an on-condition of an assocation.

The 1: when using a filter for an association tells the compiler, that the association gets a to 0..1 cardinality when the filter is applied. Otherwise you would get a warning that the cardinality of your view might change by following the assocation.

Associations can be used within CDS, from OpenSQL or by exposing then via OData.

Regards, Thomas