PL/SQL - DBMS Output

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In this chapter, we will discuss the DBMS Output in PL/SQL. The DBMS_OUTPUT is a built-in package that enables you to display output, debugging information, and send messages from PL/SQL blocks, subprograms, packages, and triggers. We have already used this package throughout our tutorial.

Let us look at a small code snippet that will display all the user tables in the database. Try it in your database to list down all the table names −

BEGIN 
   dbms_output.put_line  (user || ' Tables in the database:'); 
   FOR t IN (SELECT table_name FROM user_tables) 
   LOOP 
      dbms_output.put_line(t.table_name); 
   END LOOP; 
END; 
/ 

DBMS_OUTPUT Subprograms

The DBMS_OUTPUT package has the following subprograms −

S.No	Subprogram & Purpose
1	DBMS_OUTPUT.DISABLE; Disables message output.
2	DBMS_OUTPUT.ENABLE(buffer_size IN INTEGER DEFAULT 20000); Enables message output. A NULL value of buffer_size represents unlimited buffer size.
3	DBMS_OUTPUT.GET_LINE (line OUT VARCHAR2, status OUT INTEGER); Retrieves a single line of buffered information.
4	DBMS_OUTPUT.GET_LINES (lines OUT CHARARR, numlines IN OUT INTEGER); Retrieves an array of lines from the buffer.
5	DBMS_OUTPUT.NEW_LINE; Puts an end-of-line marker.
6	DBMS_OUTPUT.PUT(item IN VARCHAR2); Places a partial line in the buffer.
7	DBMS_OUTPUT.PUT_LINE(item IN VARCHAR2); Places a line in the buffer.

Example

DECLARE 
   lines dbms_output.chararr; 
   num_lines number; 
BEGIN 
   -- enable the buffer with default size 20000 
   dbms_output.enable; 
   
   dbms_output.put_line('Hello Reader!'); 
   dbms_output.put_line('Hope you have enjoyed the tutorials!'); 
   dbms_output.put_line('Have a great time exploring pl/sql!'); 
  
   num_lines := 3; 
  
   dbms_output.get_lines(lines, num_lines); 
  
   FOR i IN 1..num_lines LOOP 
      dbms_output.put_line(lines(i)); 
   END LOOP; 
END; 
/  

When the above code is executed at the SQL prompt, it produces the following result −

Hello Reader! 
Hope you have enjoyed the tutorials! 
Have a great time exploring pl/sql!  

PL/SQL procedure successfully completed.