大多数数据库支持的一种方法是使用递归CTE。确切的语法可能会有所不同，但想法是：

with cte as (
      select loannum, document, cnt_repeat, 1 as lev
      from t
      union all
      select loannum, document, cnt_repeat, lev + 1
      from cte
      where lev < cnt_repeat
     )
select loannum, document, cnt_repeat
from cte;