Mongodb Group Summation With Window Functions
MongoDB aggregation pipeline groups data by GRP, sorts by seq within group, sums score fields, and writes sum into x field in last row of each group.
The data of a collection (named grp_core) in the Mongdb database is as follows:
[
{ "grp": "A", "seq": 1, "score": 1, x: 0 },
{ "grp": "A", "seq": 2, "score": 3, x: 0 },
{ "grp": "A", "seq": 3, "score": 2, x: 0 },
{ "grp": "A", "seq": 4, "score": 4, x: 0 }
{ "grp": "B", "seq": 1, "score": 5, x: 0 },
{ "grp": "B", "seq": 2, "score": 2, x: 0 },
{ "grp": "B", "seq": 3, "score": 4, x: 0 },
{ "grp": "B", "seq": 4, "score": 3, x: 0 }
]
Requirement: Group by GRP, sort by seq within the group, sum the score fields of each group, and write the sum result into...