Oracle return exit continue

常在循环体中看到下面3种语句:

• return
• exit
• continue

举例说明

啥都没有

-- none 
begin
  for i in 1 .. 10 loop
    if i < 5 then
      dbms_output.put_line('i < 5, i = ' || to_char(i));
    else
      dbms_output.put_line('i >= 5, i = ' || to_char(i));
    end if;
  end loop;
  dbms_output.put_line('最外层');
end;

-- 输出
i < 5, i = 1
i < 5, i = 2
i < 5, i = 3
i < 5, i = 4
i >= 5, i = 5
i >= 5, i = 6
i >= 5, i = 7
i >= 5, i = 8
i >= 5, i = 9
i >= 5, i = 10
最外层

使用return

-- return
begin
  for i in 1 .. 10 loop
    if i < 5 then
      dbms_output.put_line('i < 5, i = ' || to_char(i));
    else
      return; -- return
      dbms_output.put_line('i >= 5, i = ' || to_char(i));
    end if;
  end loop;
  dbms_output.put_line('最外层');
end;

-- 输出
i < 5, i = 1
i < 5, i = 2
i < 5, i = 3
i < 5, i = 4

可以看出 return 的作用是直接返回了,直接结束了整个最外层语句块 begin & end /函数/存储过程.

使用exit

-- exit
begin
  for i in 1 .. 10 loop
    if i < 5 then
      dbms_output.put_line('i < 5, i = ' || to_char(i));
    else
      exit; -- exit
      dbms_output.put_line('i >= 5, i = ' || to_char(i));
    end if;
  end loop;
  dbms_output.put_line('最外层');
end;

i < 5, i = 1
i < 5, i = 2
i < 5, i = 3
i < 5, i = 4
最外层

可以看出 exit 的作用是跳出当前整个循环体,不再执行接下来的循环,同 c#/java 等编程语言中的 break.

使用continue

-- continue
begin
  for i in 1 .. 10 loop
    if i < 5 then
      dbms_output.put_line('i < 5, i = ' || to_char(i));
    else
      dbms_output.put_line('before continue i >= 5, i = ' || to_char(i));
      continue; -- continue
      dbms_output.put_line('after continue i >= 5, i = ' || to_char(i));
    end if;
  end loop;
  dbms_output.put_line('最外层');
end;

-- 输出
i < 5, i = 1
i < 5, i = 2
i < 5, i = 3
i < 5, i = 4
before continue i >= 5, i = 5
before continue i >= 5, i = 6
before continue i >= 5, i = 7
before continue i >= 5, i = 8
before continue i >= 5, i = 9
before continue i >= 5, i = 10
最外层

可以看出 continue 是跳过/不执行本次循环,会直接进行下一次循环.