Plsql 简明教程

PL/SQL - DBMS Output

在本章中，我们将讨论 PL/SQL 中的 DBMS 输出。 DBMS_OUTPUT 是一个内置包，用于显示输出、调试信息，以及从 PL/SQL 块、子程序、包和触发器发送消息。我们在整个教程中都已使用过此包。

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.

我们一起来看一下一个小代码段，它将显示数据库中的所有用户表。尝试在数据库中运行它，以列出所有表名：

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

DBMS_OUTPUT 包具有以下子程序：

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

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;
/

当以上代码在 SQL 提示符下执行时，它会生成以下结果：

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.