Using DBMS_OUTPUT to Print Messages in Oracle Procedures

In Oracle, DBMS_OUTPUT is a package that allows you to print messages from PL/SQL code, such as procedures and functions. This can be useful for debugging purposes or to display information to the user. In this tutorial, we will cover how to use DBMS_OUTPUT to print messages in Oracle procedures.

Enabling DBMS_OUTPUT

To see the output of DBMS_OUTPUT, you need to enable it in your SQL client tool. The way to do this varies depending on the tool you are using. Here are a few examples:

• In SQL*Plus, use the command SET SERVEROUTPUT ON [SIZE N|UNLIMITED]. For example: SET SERVEROUTPUT ON SIZE 30000;
• In Oracle SQL Developer, go to View | DBMS Output and click on the green plus icon to enable DBMS Output for a particular session.

Printing Messages with DBMS_OUTPUT

To print a message using DBMS_OUTPUT, you can use the PUT_LINE procedure. This procedure takes a string as an argument and prints it to the output buffer.

Here is an example of how to use DBMS_OUTPUT.PUT_LINE:

BEGIN
  DBMS_OUTPUT.PUT_LINE('Hello, World!');
END;
/

This will print the message "Hello, World!" to the output buffer.

Printing Variables with DBMS_OUTPUT

To print variables using DBMS_OUTPUT, you need to concatenate them with a string using the || operator. Here is an example:

DECLARE
  v_name VARCHAR2(10) := 'John';
BEGIN
  DBMS_OUTPUT.PUT_LINE('Hello, ' || v_name);
END;
/

This will print the message "Hello, John" to the output buffer.

Printing Rows from a Cursor with DBMS_OUTPUT

To print rows from a cursor using DBMS_OUTPUT, you can use a loop to iterate over the cursor and print each row. Here is an example:

DECLARE
  CURSOR c_emps IS SELECT * FROM employees;
  v_emp employees%ROWTYPE;
BEGIN
  FOR v_emp IN c_emps LOOP
    DBMS_OUTPUT.PUT_LINE(v_emp.first_name || ' ' || v_emp.last_name);
  END LOOP;
END;
/

This will print the first and last names of each employee in the employees table.

Best Practices

Here are some best practices to keep in mind when using DBMS_OUTPUT:

• Always enable DBMS_OUTPUT before running your PL/SQL code.
• Use meaningful variable names and comments to make your code easy to understand.
• Avoid printing sensitive information, such as passwords or credit card numbers.

By following these guidelines and examples, you can effectively use DBMS_OUTPUT to print messages in Oracle procedures.