Oracle PL/SQL Programming, 4th Edition

Chapter 21. I/O and PL/SQL

Many, perhaps most, of the PL/SQL programs we write need to interact only with the underlying Oracle RDBMS using SQL. However, there will inevitably be times when you will want to send information from PL/SQL to the external environment, or read information from some external source (screen, file, etc.) into PL/SQL. This chapter explores some of the most common mechanisms for I/O in PL/SQL, including the following built-in packages:

DBMS_OUTPUT

For displaying information on the screen

UTL_FILE

For reading and writing operating system files

UTL_MAIL and UTL_SMTP

For sending email from within PL/SQL

UTL_HTTP

For retrieving data from a web page

It is outside the scope of this book to provide full reference information about the built-in packages introduced in this chapter. Instead, in this chapter, we’ll demonstrate how to use them to handle the most frequently encountered requirements. Check out Oracle’s documentation for more complete coverage. You will also find Oracle Built-in Packages (O’Reilly) a helpful source for information on some of the older packages; we have put several chapters from that book on this book’s web site.

Displaying Information

Oracle provides the DBMS_OUTPUT package to give us a way to send information from our programs to a buffer. This buffer can then be read and manipulated by another PL/SQL program or by the host environment. DBMS_OUTPUT is most frequently used as a simple mechanism for displaying information on your screen.

Each user ...