ABAP Statements
Statements and Keywords
Types of statements in ABAP/4:
- Modularization Statements
- Control Statements
- Call Statements
- Operational Statements
- Database Statements
The source code of an ABAP program consists of comments and ABAP
statements.
Comments are distinguished by the preceding signs * (at the
beginning of a line) and “ (at any
position in a line).
ABAP statements always begin with an ABAP keyword and are always
concluded with a period
(.) . Statements can be several lines long; conversely, a line may
contain more than one
statement.
ABAP statements use ABAP data types and objects.
The first element of an ABAP statement is the ABAP keyword. This
determines the category of
the statements.
The different statement categories are as follows:
- Declarative Statements
These statements define data types or declare data objects which
are used by the other
statements in a program or routine. The collected declarative
statements in a program or routine
make up its declaration part.
- Modularization Statements
These statements define the processing blocks in an ABAP program.
The modularization keywords can be further divided into:
1.
Event
Keywords
We use statements containing these keywords to define event
blocks. There are no
special statements to conclude processing blocks - they end when
the next processing
block is introduced.
Examples of event keywords are: AT SELECTION SCREEN, START-OF-SELECTION,
AT USER-COMMAND
2. Defining keywords
we use statements containing these keywords to define subroutines,
function modules,
dialog modules and methods. We conclude these processing blocks
using the ENDstatements.
Examples of definitive keywords: FORM ..... ENDFORM, FUNCTION ...
ENDFUNCTION,
MODULE ... ENDMODULE.
- Control Statements
we use these statements to control the flow of an ABAP program
within a processing block
according to certain conditions.
Examples of control keywords: IF, WHILE, CASE
- Call Statements
we use these statements to call processing blocks that we have
already defined using
modularization statements. The blocks we call can either be in the
same ABAP program or in a
different program.
Examples of call keywords: PERFORM, CALL, SET USER-COMMAND, SUBMIT, LEAVE TO
These keywords process the data that we have defined using
declarative statements.
- Database Statements
These statements use the database interface to access the tables
in the central database system.
There are two kinds of database statement in ABAP: Open
SQL and Native SQL.
1.
Open
SQL
Open SQL is a subset of the standard SQL92 language. It contains
only Data Manipulation
Language (DML) statements, such as SELECT, INSERT, and DELETE. It
does not contain any
Data Definition Language (DDL) statements (such as CREATE TABLE or
CREATE INDEX).
Open SQL contains all of the DML functions from SQL92 that
are common to all of the database systems supported by SAP. It
also contains a few SAP-specific functions. ABAP programs that use only
Open SQL statements to access the database are fully portable. The
database interface converts the OPEN SQL commands into commands of the
relevant database.
2. Native SQL
Native SQL statements are passed directly from the database
interface to the database without
first being converted. It allows us to take advantage of all of
our database’s characteristics in
your programs. In particular, it allows us to use DDL operations.
The ABAP Dictionary uses
Native SQL for tasks such as creating database tables.
In ABAP programs that use Native SQL statements
are database-specific, because there is no standardized programming
interface for SQL92.
