Pl / SQL代码未提供任何输出

Question

I'm a beginner in PL/SQL Coding. This is a test program.

Can you please tell the reason for no output.

Please guide me.

create or replace package menu as
procedure show(name varchar2);

end menu;
/

create or replace package body menu as
procedure show(name varchar2) AS
new_number number;
begin
select count(*) into  new_number from stock;

dbms_output.put_line('This is output.');

end;
end menu;
/

Answer 1

You need to set Oracle to output lines to the console manually:

set serveroutput on;

This should be the first line in your code.

Answer 2

1. As others have said, SQL*Plus will only get the output from DBMS_OUTPUT if you first SET SERVEROUT ON .

2. Your code merely compiles and stores a database package on the database; you haven't actually run it. To run it you'd execute something like this:

    BEGIN menu.show('something'); END; / 

Answer 3

Please read the docs

 Operational Notes If you do not call GET_LINE, or if you do not display the messages on your screen in SQL*Plus, the buffered messages are ignored. SQL*Plus calls GET_LINES after issuing a SQL statement or anonymous PL/SQL calls. Typing SET SERVEROUTPUT ON in SQL*Plus has the effect of invoking DBMS_OUTPUT.ENABLE (buffer_size => NULL); with no limit on the output. You should generally avoid having application code invoke either the DISABLE Procedure or ENABLE Procedure because this could subvert the attempt of an external tool like SQL*Plus to control whether or not to display output. Note: Messages sent using DBMS_OUTPUT are not actually sent until the sending subprogram or trigger completes. There is no mechanism to flush output during the execution of a procedure. Exceptions DBMS_OUTPUT subprograms raise the application error ORA-20000, and the output procedures can return the following errors: Table 68-1 DBMS_OUTPUT Errors Error Description ORU-10027: Buffer overflow ORU-10028: Line length overflow Rules and Limits The maximum line size is 32767 bytes. The default buffer size is 20000 bytes. The minimum size is 2000 bytes and the maximum is unlimited. 

So SET SERVEROUTPUT ON is only for SQL*Plus.