更新时间:2022-06-23 05:31:38
您首先 $ group 在 _id:$ a与 $ sum:{1} (这基本上是你对不同a的计数) c $ c> sort 。
$ group
_id:$ a
$ sum:{1}
You first $group on _id:"$a" with $sum:{1} (this is basically your count on distinct a) then sort on the sum.
$group
_id:"$a"
$sum:{1}
sort
MongoDB相当于SQL COUNT GROUP BY
Linq to SQL相当于SUM GROUP BY SQL语句
MongoDB相当于SQL"TOP"
mongodb 相当于 sql select 'longfield' as 'a'
6.组函数(avg(),sum(),max(),min(),count())、多行函数,分组数据(group by,求各部门的平均工资),分组过滤(having和where),sql优化
linq to sql (Group By/Having/Count/Sum/Min/Max/Avg操作符)