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oraclegoto语句介绍

theoraclepl/sql goto statement is a sequential control structure available in oracle. the goto statement immediately transfers program control (called branching) unconditionally to a named statement label or block label. the statement or
the oracle pl/sql goto statement is a sequential control structure available in oracle. the goto statement immediately transfers program control (called branching) unconditionally to a named statement label or block label. the statement or label name must be unique in the block.
属于plsql控制语句,用于程序控制非条件跳至指定标签>。不易控制和维护,慎用!
二 例子:
1、简单goto 语句,判断数字是否为质数:
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declare
  p varchar2(30);
  n pls_integer := 37; -- test any integer > 2 for prime
begin
  for j in 2 .. round(sqrt(n)) loop
    if n mod j = 0 then
      -- test for prime
      p := ' is not a prime number'; -- not a prime number
      goto print_now;
    end if;
  end loop;
  p := ' is a prime number';
  >
  dbms_output.put_line(to_char(n) || p);
end;
/
2、使用null避免报错:
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declare
  done boolean;
begin
  for i in 1 .. 50 loop
    if done then
      goto end_loop;
    end if;
    > -- not allowed unless an executable statement follows
    null; -- add null statement to avoid error
  end loop; -- raises an error without the previous null
end;
/
3、使用goto分出一个环绕块:
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-- example with goto statement
declare
  v_last_name varchar2(25);
  v_emp_id    number(6) := 120;
begin
  >
  select last_name
  into v_last_name
  from employees
  where employee_id = v_emp_id;
  begin
    dbms_output.put_line(v_last_name);
    v_emp_id := v_emp_id + 5;
    if v_emp_id
      goto get_name; -- branch to enclosing block
    end if;
  end;
end;
/
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