如何使用sql获取上个月的第一天和最后一个月

I am trying to get the first day of last month like 01/01/2013, also i want to get the last day of previous month like 01/31/2013. If we are in March then i want to do the same thing like 02/01/2013 and 02/28/2013 and so on.... thanksI am trying to get the first day of last month