mongodb分组查询

通过userId分组，得到结果字段为：_id和count

db.my_solitaire.aggregate([

{$group: {_id: "$userId", count: {$sum: 1}}}

])

通过userId分组得到分组字段和其他想要的字段，得到_id，userName，count
userName 为分组外想要得到的字段

db.my_solitaire.aggregate([

{$group: {_id: "$userId", count: {$sum: 1},userName:{"$first":"$userName"}}}

])

增加时间条件

db.my_solitaire.aggregate([

{$match:{createTime:{$eq:"2023-06-13 09:00:38"}}},

{$group: {_id: "$userId", count: {$sum: 1},name:{"$first":"$userName"}}}

])