| Name | Description |
|---|---|
| $addToSet | Returns an array of all the unique values for the selected field among for each document in that group. |
| $first | Returns the first value in a group. |
| $last | Returns the last value in a group. |
| $max | Returns the highest value in a group. |
| $min | Returns the lowest value in a group. |
| $avg | Returns an average of all the values in a group. |
| $push | Returns an array of all values for the selected field among for each document in that group. |
| $sum | Returns the sum of all the values in a group. |