Database Access using Advanced Business Application Programming (ABAP)
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by Arindam Ghosh
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Open SQL

Open SQL are statements that make up a subset of Standard SQL which is fully integrated in ABAP. Open SQL consists of Data Manipulation Language (DML) which is a part of Standard SQL.

One of the ways to access the database from a program is Open SQL. These Open SQL statements are nothing but a subset of Standard SQL, which is fully integrated in ABAP. Irrespective of which database system the R/3 installation is using, they allow you to access data. When I said that, Open SQL consists of the Data Manipulation Language (DML). I meant that it allows you to read (i.e. to SELECT) and change (i.e. to INSERT, UPDATE, DELETE) data.

Moreover, Open SQL also goes beyond Standard SQL. This is to provide statements that can simplify or speed up database access in conjunction with other ABAP constructions. Apart from that, it also gives you the freedom to buffer certain tables on the application server, thereby enabling you to save excessive database access. In this case, the database interface is responsible for comparing the buffer with the database. As far as buffer storage is concerned, they may be stored in two parts: the working memory of the current work process, and the shared memory for all work processes on an application server. The data in the various buffers is synchronized at set intervals by buffer management where an R/3 system is distributed across more than one application server. It should be noted that data in the buffer is not always up to date when you are buffering the database. That is why you should only use the buffer for data which does not change often. You can specify whether a table can be buffered in its definition in the ABAP Dictionary.

Open SQL consists of a set of ABAP statements. These statements perform operations on the central database in the R/3 system. The results of the operations and any error messages which come out of it are independent of the current database system. Thus, uniform syntax and semantics for all of the database systems supported by SAP is provided by Open SQL. Regardless of the current database system, the ABAP programs, which use Open SQL statements only, will work in any R/3 system. Moreover, Open SQL statements work only with database tables that have been created in the ABAP Dictionary.

You have the freedom to combine columns belonging to different database tables to a database view (or view for short) in the ABAP Dictionary. Views are also handled in exactly the same way as database tables in Open SQL statements.

Some Open SQL keywords are as follows:

SELECT - It reads data from database tables.

INSERT - It adds rows to database tables.

UPDATE - It changes the contents of rows of database tables.

MODIFY - It inserts rows into database tables or changes the content of existing rows.

DELETE - It deletes rows from database tables.

OPEN CURSOR, FETCH, CLOSE CURSOR - It reads rows of database tables using the cursor.

Return Codes

The following two system fields are filled with return codes by all Open SQL statements:

SY-SUBRC: The system field SY -SUBRC contains the value 0 after every Open SQL statement if the operation was successful. When a value is other than 0, then it is unsuccessful.

SY-DBCNT: The system field SY-DBCNT contains the number of database lines processed after an open SQL statement.

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