循环语句【PL/SQL】

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1. loop【至少执行一次循环体类似do{}while();】

-- 编写一个过程，可输入用户名，并循环添加3个用户到users表
-- users表中，用户编号从1开始增加、
declare
v_num number :=1;
v_name users.username%type :='0';
begin
  loop
    insert into users values(v_num,v_name);
    exit when v_num=3;
    v_num:=v_num+1;
    v_name:=v_name||'0';
  end loop;
end;

2. while

declare
v_num number :=1;
v_name users.username%type :='1';
begin
  while v_num<=3 loop
    insert into users values(v_num,v_name);
    v_num:=v_num+1;
    v_name:=v_name||'0';
  end loop;
end;

3. for【步长为1，不够灵活】

declare
v_num number :=1;
v_name users.username%type :='fo';
begin
  for i in reverse 1..3 loop
    insert into users values(i,v_name);
    --v_num:=v_num+1;
    v_name:=v_name||'0';
  end loop;
end;