Databases Reference
In-Depth Information
Third-generation languages (3GLs)
Programmers can interact with the Oracle Database from C, C++, Java, or COBOL by
embedding SQL in those applications. Prior to compiling the applications using a plat‐
form's native compilers, you must run the embedded SQL code through a precompiler.
The precompiler replaces SQL statements with library calls the native compiler can
accept. Oracle provides support for this capability through optional “programmer”
precompilers for C and C++ using Pro*C and for COBOL using Pro*COBOL. In recent
Oracle versions, Oracle features SQLJ, a precompiler for Java that replaces SQL state‐
ments embedded in Java with calls to a SQLJ runtime library, also written in Java.
Database drivers
All versions of Oracle include database drivers that allow applications to access Oracle
via ODBC (the Open Database Connectivity standard) or JDBC (the Java Database
Connectivity open standard). Also available are Oracle Data Access Connectors
(ODAC) for .NET. ODAC provides a data provider for .NET, providers for ASP.NET
and .NET stored procedures, and tools for developers using Visual Studio.
The Oracle Call Interface
If you're an experienced programmer seeking optimum performance or a finer level of
control, you may choose to define SQL statements within host-language character
strings and then explicitly parse the statements, bind variables for them, and execute
them using the Oracle Call Interface (OCI). OCI is a much more detailed interface that
requires more programmer time and effort to create and debug. Developing an appli‐
cation that uses OCI can be time-consuming, but the added functionality and incre‐
mental performance gains could make spending the extra time worthwhile.
In certain programming scenarios, OCI improves application performance or adds
functionality. For instance, in high-availability implementations in which multiple sys‐
tems share disks using Real Application Clusters, you could write programs using OCI
that allow users to reattach to a second server transparently if the first fails. As of Oracle
Database 12
c
, the Transaction Guard API to the database can be used in order to preserve
guaranteed commits where data is accessed via OCI (or alternatively via JDBC thin
drivers, OOCI, or ODP.NET).
National Language Support
National Language Support (NLS) provides character sets and associated functionality,
such as date and numeric formats, for a variety of languages. The initial release of Oracle
Database 12
c
features Unicode 6.1 support. All data may be stored as Unicode, or select
columns may be incrementally stored as Unicode. UTF-8 encoding and UTF-16 en‐
coding provide support for more than 57 languages and 200 character sets. Extensive
localization is provided (for example, for data formats), and customized localization
can be added through the Oracle Locale Builder. Oracle includes a Globalization Toolkit
for creating applications that will be used in multiple languages.
