你好，

研究'使用X AS'并通过2-3个简单步骤构建您需要的步骤，每个步骤都可以理解。

Study 'WITH X AS' and build what you need to get with 2-3 simple steps, each of which you can understand.

并且..我无法理解为什么在源数据上

And... I can't understand why on source data

2017 03      345

2017 03      346

2017 03      347

2017 03     345
2017 03     346
2017 03     347

摸索的结果假设是 

the result of groping suppose to be 

2017 03      347

您是否选择MAX（ID）作为第三列的结果？

Do you select MAX(ID) as result for third column?