In ABAP programming language there are two types of SQL used: i) Open SQL ii)Native SQL . Open SQL allows you to access the database tables declared in the ABAP dictionary regardless of the database platforms that the R/3 system is used Open SQL consists of a set of ABAP statements that perform operations on the central database in the R/3 system. The results of the operations and any error messages are independent of the database system in use. Open SQL thus provides a uniform syntax and semantics for all of the database systems supported by SAP. Basic Open SQL Commands: Select , Insert , Update, Modify , Delete, Fetch , Open cursor, Close cursor. Native SQL allows to use database-specific SQL statements in an ABAP/4 program. This means that you can use database tables that are not administered by ABAP dictionary, and therefore integrate data that is not part of the R/3 system.