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

Native SQL is very important as it allows you to execute nearly all available statements through the SQL programming interface (usually known as SQL Call Interface or similar) for directly executing SQL program code (using EXEC IMMEDIATE or a similar command). The statements that are not supported are listed in the following section:

·         Native SQL and the Database Interface,

·         Native SQL and Transactions

·         Native SQL and the Database Interface

Native SQL statements bypass the R/3 database interface. With the database buffer on the application server, there is no table logging, and no synchronization. Therefore, you should use Open SQL to change database tables declare in the ABAP dictionary wherever possible. Since the columns contain extra database specific length information for the column tables declared in the ABAP dictionary, containing long columns with the type LCHAR or LRAW should only be addressed using Open SQL. Native SQL may not produce the correct result, as it does not take this information into account. Native SQL does not support automatic client handling. Instead, you must treat a client field like any other field

Native SQL and Transactions

One should not use any transaction control statement such as COMMIT, ROLLBACK WORK, or any statements that set transaction parameters using Native SQL to ensure that transaction in the R/3 System are consistent.

ABAP Dictionary

The ABAP Dictionary is nothing but a part of the ABAP Workbench. It allows you to create and administer database tables. There are no statements from the DDL part of Standard SQL in Open SQL. It should be noted that normal application programs should not create or change their own database tables.

To create and change database tables, the ABAP Dictionary has to use the DDL part of Open SQL. Besides this, it also administers the ABAP Dictionary in the database. In addition, the ABAP Dictionary contains meta-descriptions of all database tables in the R/3 system. Here, only database tables appears in the Dictionary, which you have created using the ABAP Dictionary. Open SQL statements can only access tables, which exists in the ABAP Dictionary.

Authorization and Consistency Checks

With regard to authorization and consistency checks, the DCL part of Standard SQL is not used in R/3 programs. Whereas, the work processes which are within the R/3 system are logged into the database system as users with full rights. By using the R/3 authorization concept, the authorizations of programs or users to read or change database tables is administered within the R/3 system. In addition, transactions must equally ensure their own data consistency using the R/3 locking concept.

The R/3 lock concept allows you to monitor your system with regards to lock logics. The R/3 lock concept works closely together with the R/3 updates.

As an example, say that a travel agent wants to book a flight for a customer who wants to fly to a particular city with a certain airline on a certain day. If there are still available seats on the flight, then the booking will be possible, otherwise it will lead to overbooking. Hence, the database entry corresponding to the flight must be locked against access from other transactions to avoid the possibility of overbooking. This is because two agents might both be doing this same thing at the same time, and we need to make sure that we don't overbook.

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