Get Example source ABAP code based on a different SAP table
• DEFINE JOIN DEPENDENCY RULE ABAP_DDIC_STATEMENT
ABAP_DDIC_DDL - DEFINE JOIN DEPENDENCY RULE
ABAP_SYNTAX DEFINE JOIN DEPENDENCY RULE drul ON dbtab1, dbtab2 IF { cond_pattern } THEN { derived_cond }
What does it do? Variant of the Dictionary DDL statement DEFINE DEPENDENCY RULE used to define a join dependency rule . A join dependency rule can be defined for exactly two database tables dbtab1 and dbtab2, separated by a comma. It derives an additional join condition derived_cond from the pattern cond_pattern. When two DDIC database tables joined by a join expression are read, the SAP HANA database optimizer finds the pattern in the ON condition of the expression and, if necessary, adds the additional join condition AND to this condition. If any further additional conditions are defined by filter dependency rules for one of the two database tables, these rules are also applied to the other DDIC database table, if they apply to the columns specified in the join condition. <(>cond_pattern<)> In cond_pattern, a pattern from a relational expression can be specified in the curly brackets after IF as follows: lhs = rhs $[AND lhs = rhs ...$] Comparisons with the operator = joined using AND are possible. Joins using OR or negations using NOT are not possible.
The following can be specified as the left side lhs of the comparison:
dbtab1.column or dbtab2.column for a column column of the DDIC database tables dbtab1 or dbtab2.
The following can be specified as the right side rhs of the comparison:
dbtab1.column or dbtab2.column for a column column of the DDIC database tables dbtab1 or dbtab2.
An untyped character literal or an untyped numeric literal. This syntax is the same as in untyped literals in ABAP CDS.
A numbered placeholder $1, $2, ... <(>derived_cond<)> In derived_cond, a template for a relational expression can be specified in the curly brackets after THEN as follows: lhs =$| < $|>$| < =$|>= rhs $[OR lhs =$| < $|>$|<(> <<)>=$|>= rhs ...$] Single comparisons can be placed in parentheses ( ). Negations using NOT are not possible.
The following can be specified as the left side lhs of a comparison:
dbtab1.column or dbtab2.column for a column column of the database table dbtab1 or dbtab2.
The following can be specified as the right side rhs of a comparison:
dbtab1.column or dbtab2.column for a column column of the database table dbtab1 or dbtab2.
An untyped character literal or an untyped numeric literal. This syntax is the same as in untyped literals in ABAP CDS .
A numbered placeholder $1, $2, ..., which must also be specified in cond_pattern. When the condition is added, the operand for the condition is inserted into this placeholder. The same placeholder for the same operand value must exist in the pattern cond_pattern.
Built-in functions in ABAP Dictionary in ABAP CDS syntax.
Simple case distinctions in ABAP CDS syntax.
Latest notes:
It cannot be guaranteed that the SAP HANA database optimizer finds the pattern cond_pattern. This is why the additional condition derived_cond must not modify the result set of the original query. It is technically possible to modify the result set with a dependency rule, but should be avoided since it produces undefined behavior in cases where the SAP HANA database optimizer finds the pattern cond_pattern in some reads but not in others.
The additional condition for a query can be viewed in the SQL Trace tool (transaction ST05) by choosing Display Execution Plan . ABAP_HINT_END
Example ABAP Coding
The following dependency rules are defined: DEFINE FILTER DEPENDENCY RULE demo_drul_3 ON demo_parts_3 IF { demo_parts_3.value >= 30 } THEN { demo_parts_3.area >= 3 } DEFINE FILTER DEPENDENCY RULE demo_drul_4 ON demo_parts_3 IF { demo_parts_3.value < 40 } THEN { demo_parts_3.area < 4 } DEFINE JOIN DEPENDENCY RULE demo_drul_5 ON demo_parts_3, demo_parts_4 IF { demo_parts_3.client = demo_parts_4.client AND demo_parts_3.id = demo_parts_4.id AND demo_parts_3.value = demo_parts_4.value } THEN { demo_parts_3.area = demo_parts_4.area } The program DEMO_DEPENDENCY_RULE_3 uses the following SELECT statement to access DEMO_PARTS_3 and DEMO_PARTS_4: SELECT demo_parts_3~id, demo_parts_3~value, demo_parts_4~text FROM demo_parts_3 INNER JOIN demo_parts_4 ON demo_parts_3~id = demo_parts_4~id AND demo_parts_3~value = demo_parts_4~value WHERE demo_parts_3~value >= 30 AND demo_parts_3~value < 40 ORDER BY demo_parts_3~id INTO TABLE @DATA(result). The SAP HANA database optimizer adds the following condition to the ON condition implicitly: AND demo_parts_3~area = demo_parts_4~area It also adds the following filter conditions to the WHERE condition implicitly: AND demo_parts_3~area >= 3 AND demo_parts_3~area < 4 AND demo_parts_4~area >= 3 AND demo_parts_4~area < 4 If the data in the DDIC database tables is structured correctly, the dependency rules do not modify the result set. ABAP_EXAMPLE_END
