Modern ABAP Open SQL: Host Variables, Expressions and Pushdown

Open SQL is ABAP's database access language. Modern releases expanded it far beyond the older SELECT field list/WHERE syntax, while retaining ABAP-level semantics such as automatic client handling and DDIC-aware typing. The @ prefix clearly separates ABAP host variables from database fields. Expressions can calculate values in the SELECT list, CASE can derive fields, aggregates can summarize data, and CTEs can structure complex reads. These features support code pushdown without jumping directly to native SQL or AMDP for every nontrivial query.

Use modern Open SQL for ordinary transactional/reporting reads and writes whenever the requirement can be expressed cleanly and the data source is available through permitted tables or CDS entities. Prefer it over nested SELECT loops and over pulling broad datasets into ABAP for filtering/calculation. Reach for CDS when the model should be reusable and semantically annotated across consumers; reach for AMDP only when SQLScript-specific capability is genuinely required.

Open SQL sits between ABAP application logic and the database. On S/4HANA it is optimized for HANA but remains an ABAP platform abstraction. It can consume CDS entities, call supported database functions, and cooperate with table buffering where relevant. ATC checks can flag problematic SQL patterns, while ST05 and SQL Monitor show actual runtime behavior. Clean-core restrictions affect which data sources are released, not the basic language features.

An older report selects a large transaction table, loops in ABAP to calculate a category, then filters and totals the surviving rows. A modern Open SQL version moves the category calculation into CASE, pushes the filter into WHERE/HAVING, and uses SUM/GROUP BY so only the final aggregated rows cross to the application server. The code becomes shorter and the database performs the set operation it is designed for. ST05 confirms the reduced transferred-row count.

Modern Open SQL is the default database access language for S/4HANA ABAP development and is fully aligned with HANA pushdown. ABAP Cloud further restricts the data sources and APIs that code may consume, but it uses the same modern SQL style. Classic syntax can still exist in converted code, yet new development should use current syntax and released data models.

ABAP developers own query design, typing, and exception/result handling. Architects decide when logic deserves a reusable CDS layer or AMDP. Functional/data owners define semantics such as aggregation grain and join cardinality; those cannot be inferred safely from table names alone.

The JOIN versus FAE and SQL performance topics cover common query choices. CDS versus Open SQL versus AMDP is the next architectural decision when logic grows beyond one program.

Production verification: Capture program/include and source line, selection/variant, realistic data volume, execution count, transferred rows, elapsed/DB time and the before/after trace. Use ST05/SQLM for SQL evidence and SAT/ST12 for application runtime; optimize query shape and call frequency before changing indexes or adding parallelism.

Operational readiness: For production readiness of Modern ABAP Open SQL: Host Variables, Expressions and Pushdown, add one reproducible test case with realistic data volume and boundary values, one negative test that proves the failure contract, and one operational check that a support developer can run without changing productive data. Record the exact program/class/function and release-dependent API assumptions. Where the topic affects performance or transaction consistency, compare evidence before and after the change instead of relying on coding folklore or a single sandbox execution.