Create a simple store procedure in oracle 12c

Question

I am looking to create a simple store procedureto return a list of all user names in a table called dba_users.

The select I am using is:

SELECT username FROM dba_users

When I create a PROCEDURE with the following syntax it is created, but fails to execute:

CREATE OR REPLACE PROCEDURE user_list_display
IS
BEGIN
    SELECT username FROM dba_users
END;

For this I get

ORA-00900: invalid SQL statement:
EXECUTE user_list_display;

Answer 1

you had better using an implicit cursor with dbms_output.put_line :

SQL> set serveroutput on;
SQL> CREATE OR REPLACE PROCEDURE user_list_display IS
BEGIN
FOR c in ( SELECT username FROM dba_users )
LOOP
 dbms_output.put_line(c.username);
END LOOP;
END;
/
SQL> exec user_list_display;

Answer 2

In Oracle12c, You can use DBMS_SQL.RETURN_RESULT .

CREATE OR REPLACE PROCEDURE user_list_display
IS
v_cursor   SYS_REFCURSOR;
BEGIN
OPEN v_cursor FOR SELECT username FROM dba_users;
    DBMS_SQL.RETURN_RESULT ( v_cursor );
END;
/

Then execute it as

EXEC user_list_display;

In lower versions,from SQL* Plus (or execute as script in SQL Developer ), you may use a REFCURSOR OUT variable and PRINT to display the result.

CREATE OR REPLACE PROCEDURE user_list_display( output OUT SYS_REFCURSOR )
IS
BEGIN
OPEN output FOR SELECT username FROM dba_users;
END;
/

You may run these 3 lines whenever you want to see the output.

VARIABLE output REFCURSOR
EXEC user_list_display(:output)
PRINT output