oracle plsql中的动态goto

Question

I have a procedure that updates ~700 rows from a table based on certain dates. I want, if the procedure crashes from some reason to restart the procedure from where it left, not from the beginтing ( ex: go to row214).

If I try something like this:

begin

goto &label;

<N1>;

dbms_output.put_line(1);

<N2>;

dbms_output.put_line(2);

end;

it works, but that will presume human interaction, and I would want the procedure to do this automatically.

How can I do something like this without the ampersand(&)? If I declare the label as a variable, it doesn't work, or I don't know how to make it work.

Answer 1

You cannot do a "dynamic GOTO" in a static PL/SQL block. The reason is that any argument that follows the GOTO keyword will be interpreted as the label you want to jump to, not as an expression that will evaluate to the label.

About the closest you'll get is this:

declare 
  l_label VARCHAR2(30) := 'N2';
BEGIN

 CASE l_label
   WHEN 'N1' THEN GOTO N1;
   WHEN 'N2' THEN GOTO N2;
   ELSE raise_application_error (-20001, 'Unknown label: ' || l_label);
 END CASE;

 <<N1>>
  DBMS_OUTPUT.put_line (1);

 <<N2>>
  DBMS_OUTPUT.put_line (2);
END;

Answer 2

While you cannot do this in static PL/SQL, your use of ampersand (&) implies that you might be using SQL*Plus and merely want to avoid having a human have to type in the value of the label at runtime.

In SQL*Plus, you can do this.

column label_value old_value label;
set termout off
REM Replace the following SQL with something that will get the correct label.
select 'N2' label_value FROM dual;
set termout on
set verify off

set serveroutput on

begin
  goto &label;
  <<N1>>
  dbms_output.put_line('N1');
  <<N2>>
  dbms_output.put_line('N2');
end;
/