如标题中所指定，我需要编写查询以获取特定于结果的行（序列号列表），这些行每个月只有一个状态为“过期”（月数将在end_time上计算）。例如： 我的桌子是
sr_num, start_time, end_time , renew_date, status
s1 , 15-01-2016, 15-01-2017, 15-01-2016, purchase
s1 , 15-01-2016, 15-01-2017, 15-01-2016, expired
s2 , 15-01-2016, 15-01-2017, 15-01-2016, purchase
s2 , 15-01-2016, 15-01-2017, 15-01-2016, expired
s2 , 20-01-2017, 20-01-2018, 20-01-2017, renew
s3 , 15-01-2016, 15-01-2017, 15-01-2016, purchase
s3 , 15-01-2016, 15-01-2018, 10-01-2017, extends
条件：
- “按sr_num，end_times分组”
- 状态只能在每个月过期
结果应该仅是一行s1，15-01-2016、15-01-2017、15-01-2016，已过期
