CDS Table Functions: when a CDS view isn't enough and you need SQLScript

Regular CDS views are declarative: a SELECT with joins, associations and aggregations. Powerful, but there’s a ceiling. When the logic demands procedural SQLScript (loops, intermediate tables, something a define view can’t express) CDS Table Functions come in. They’re CDS objects that extend modeling with HANA’s code-pushdown capability, implemented by an AMDP method.

Two pieces wired together

A Table Function isn’t a single object: it’s two artifacts pointing at each other.

• The CDS object: declares the input parameters and, in RETURNS, the tabular structure. The IMPLEMENTED BY METHOD clause names the class and AMDP method that resolve it.
• The AMDP class: implements the logic in SQLScript. The definition is marked FOR TABLE FUNCTION with the CDS name; the implementation uses BY DATABASE FUNCTION FOR HDB LANGUAGE SQLSCRIPT.

flowchart TB
 Q["Consumer (SELECT or CDS view)"] --> TF["CDS Table Function RETURNS + parameters"]
 TF -->|"IMPLEMENTED BY METHOD"| M["AMDP method FOR TABLE FUNCTION"]
 M --> S["SQLScript BY DATABASE FUNCTION FOR HDB"]
 S --> HANA[("HANA")]

The CDS object looks like this:

@ClientDependent: true
define table function ZTF_SALES_BY_CARRIER
  with parameters @Environment.systemField: #CLIENT
                  p_clnt : abap.clnt
  returns { client   : s_mandt;
            carrid   : s_carr_id;
            total    : s_price; }
  implemented by method zcl_tf_sales=>get_sales_by_carrier;

And the AMDP method that implements it:

METHOD get_sales_by_carrier
  BY DATABASE FUNCTION FOR HDB
  LANGUAGE SQLSCRIPT
  OPTIONS READ-ONLY
  USING sflight.

  RETURN SELECT mandt AS client,
                carrid,
                SUM( price ) AS total
           FROM sflight
          WHERE mandt = :p_clnt
          GROUP BY mandt, carrid;
ENDMETHOD.

The best part comes next: that Table Function is consumed like any CDS source. You can SELECT from it or use it inside another CDS view. You model as CDS, you execute as SQLScript.

The detail that trips people up: SELECT-OPTIONS

Table Functions do not support SELECT-OPTIONS filtering natively. It’s a real limitation that surprises everyone on their first project. The pattern to solve it:

• Declare a long CHAR parameter in the Table Function that carries the dynamically built filter.
• In the AMDP method apply that filter with the APPLY_FILTER function.
• In the program, build the SELECT-OPTIONS string with CL_SHDB_SELTAB=>COMBINE_SELTABS, which returns the filter as a STRING ready to pass into the parameter.

It isn’t elegant, but it’s the supported path, and once you’ve wired it up it’s reusable.

A Table Function is the right answer to a very specific question: “I need SQLScript but I want to consume it as CDS”. If you’re not asking that question, you don’t need it.

That closes the trio of code-to-data, AMDP and Table Functions. The next posts get practical: the golden rule of SELECT and HANA’s tooling to measure instead of guess.