Chapter 2. Creating and Running pl/sql Code

Before exploring the "meat and potatoes" of writing PL/SQL programs, you might benefit from some practical information about how to compile and run those programs. This chapter surveys a range of tools, in particular SQL*Plus, from which you can invoke your PL/SQL programs, and provides the specifics you'll need to get started.

If you already have some experience with database programming, you probably realize that there are lots of different ways and places to use SQL (Structured Query Language). Well, the same is true for PL/SQL; not only can you invoke it from a variety of other languages, it can execute in two different runtime environments:

• "Inside" the Oracle database server, as stored code. If you call PL/SQL from SQL*Plus, Java, or any other language, this is typically where it's going to run.

• In one of Oracle's application development environments such as Oracle Forms or Oracle Reports, as a program that executes on a client computer. (Alternately, these tools can run on a "middle tier," operated across the network from a browser-only or "thin" client.)

Let's begin by looking at the first option, running on the Oracle server. Here you have additional options for the front end from which you launch your code. Some of the most popular programming tools include:

• Oracle's command-line tool, SQL*Plus, which connects to an Oracle server where you can run PL/SQL statements.

• A host language such as C, C++, Java, Visual Basic, COBOL, Ada, or FORTRAN, for which Oracle provides a runtime library and/or precompiler that allows you to embed SQL and PL/SQL calls into your program.

Because the number of execution tools at your disposal will probably far exceed your time to assimilate them, it makes sense to concentrate on one or two, and learn them really well. So, while this chapter shows some examples of using PL/SQL with a variety of tools, the main concentration is on SQL*Plus.

2.1 Sql*Plus

The granddaddy of Oracle front ends, Oracle's SQL*Plus provides a command-line interpreter for both SQL and PL/SQL. That is, it accepts database statements from the user, then sends them off to the Oracle server, and finally displays the results.

Often maligned for its primitive user interface, SQL*Plus is one of my favorite Oracle tools. I actually like the lack of fancy gizmos or complicated menus. When I started using Oracle (circa 1986), this product's predecessor was boldly named UFI—User Friendly Interface. Almost two decades later, even Oracle9i's version of SQL*Plus is still unlikely to win any user friendliness awards, but at least it doesn't crash very often.

Today there are several different styles ofexecuting SQL*Plus:

As a console program

This is a program that runs from a shell or command prompt^[1] (an environment that is sometimes called a console).

^[1] Oracle calls this the "command-line interface" version of SQL*Plus, but I find that somewhat confusing, because two of the four styles provide a command-line interface.

As a pseudo-GUI program

This form of SQL*Plus is available only on Microsoft Windows. I call it a "pseudo-GUI" because it looks pretty much like the console program but with bitmapped fonts; few other features distinguish it from the console program. In fact, Oracle is already phasing out support for this product, with even "extended" support terminating in September 2005.

Via iSQL*Plus (in Oracle9i or later)

This program executes from a web browser connected to a middle-tier machine running Oracle's HTTP server and iSQL*Plus server.

Via SQL*Plus Worksheet

This is merely a Java GUI front end on the console version of SQL*Plus. Although it does maintain some statement history, there is little else to commend this version.

Figure 2-1 is a screen shot of a SQL*Plus console-style session.