Investigate Your Database and Application Environment
02.05.2010 by admin - 0 CommentPosted in Oracle
This is a paper-based exercise, with no specific solution.
Attempt to identify the user processes, application servers, and database servers used in your environment. Try to work out where the SQL is being generated and where it is being executed. Bear in mind that usually the user processes used by end users will be graphical and will frequently go through application servers; the database administration and development staff will often prefer to use client-server tools that connect to the database server directly.
Development Tools and Languages
The Oracle server technologies include various facilities for developing applications,some existing within the database, others external to it.
Within the database, it is possible to use three languages. The one that is unavoidable, and the subject of this book, is SQL. SQL is used for data access, but it cannot be used for developing complete applications. It has no real facilities for developing user interfaces, and it also lacks the procedural structures needed for manipulating rows individually. The other two languages available within the database fill these gaps. They are PL/SQL and Java. PL/SQL is a third-generation language (3GL) proprietary to Oracle. It has the usual procedural constructs (such as if-then-else and looping) and facilities for user interface design. In the PL/SQL code,one can embed calls to SQL. Thus, a PL/SQL application might use SQL to retrieve one or more rows from the database, then perform various actions based on their content, and then issue more SQL to write rows back to the database. Java offers a similar capability to embed SQL calls within the Java code. This is industry standard technology: any Java programmer should be able write code that will work with an Oracle database (or indeed with any other Java-compliant database.)
Other languages are available for developing client-server applications that run externally to the database. The most commonly used are C and Java, but it is possible to use most of the mainstream 3GLs. For all these languages, Oracle Corporation provides OCI (Oracle Call Interface) libraries that let code written in these languages establish sessions against an Oracle database and invoke SQL commands. Many organizations will not want to use a 3GL to develop database applications.
Oracle Corporation provides rapid application development tools as part of the Oracle Developer Suite, and there are many third-party products. These can make programmers far more productive than if they were working with a 3GL. Like the languages, all these application development tools end up doing the same thing: constructing SQL statements that are sent to the database server for execution.
