数据库里怎么存储这种数据？

就是这种两层甚至多层的数据，除了存成定期存款_三个月，定期存款_半年这样的还有别的方法吗？
------解决方案--------------------
date                 type                             id                   value
2008/10/09            1                               null                  0.72
2008/10/09            2                               1                     3.15
2008/10/09            2                               2                     3.55
2008/10/09            2                               3                     3.87
............
2008/10/09            2                               6                     5.58