SAP BUFFER EXPRESSIONS

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ABAP_BUFFER - SQL Expressions
The evaluation of SQL expressions as well as the execution of built-in functions as operands of such expressions is usually evaluated on the database and their use inevitably leads to the bypassing of table buffering. However, the following expressions and functions also have an implementation in the table buffer and their use in read accesses (even nested) does not lead to the bypassing of table buffering.

Elementary SQL expression

Built-in SQL function

Numeric functions ABS, CEIL, DIV, FLOOR, and MOD

String functions CONCAT, CONCAT_WITH_SPACE, and SUBSTRING

Null value function COALESCE (in the SELECT list only)

Arithmetic expressions

Case distinctions (in the SELECT list only)
The expressions and functions can be used in both SELECT lists and in WHERE clauses.
If a catchable exception is raised when an SQL expression is evaluated in the table buffer, it is wrapped by the class CX_SY_OPEN_SQL_DB and can be handled using this class. The attribute PREVIOUS of the associated exception object is then given the name of the original exception class.

Latest notes:

When an SQL expression is evaluated in the table buffer, the same results are produced as on the database and not as in the corresponding ABAP evaluation. The following are some examples:

Evaluations of the functions DIV and MOD that are not the same as calculations with the identically named ABAP operators.

Operands of the type SSTRING that do not have trailing blanks on the database, unlike in ABAP.

Any null values produced as results of nested expressions, for example in the COALESCE function or in comparisons , are handled as null values.

The result of a relational expression with columns that contain null values is unknown, except in the case of the expression IS $[NOT$] NULL.

If an SQL expression can be evaluated in the table buffer, any internal tables used as data sources of a query can also be evaluated on AS ABAP rather than their content having to be transported to the database.
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