This is the sample of my mongodb document( try to use jsonformatter.com to analyse it):

```
{"_id":"6278686","playerName":"Rohit Lal","tournamentId":"197831","score":[{"_id":"1611380","runsScored":0,"ballFaced":0,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"-","catches":["Mohit Mishra"],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1602732","runsScored":0,"ballFaced":0,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"-","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1536514","runsScored":1,"ballFaced":3,"fours":0,"sixes":0,"strikeRate":33.33,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"run out Sameer Baveja","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1536474","runsScored":2,"ballFaced":7,"fours":0,"sixes":0,"strikeRate":28.57,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"c Rajesh b Prasad Naik","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1536467","runsScored":0,"ballFaced":0,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"-","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1500825","runsScored":0,"ballFaced":0,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"-","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1461428","runsScored":18,"ballFaced":6,"fours":1,"sixes":2,"strikeRate":300,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"not out","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1461408","runsScored":0,"ballFaced":1,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"c Sudhir b Vinay Kasat *vk*","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1451175","runsScored":0,"ballFaced":0,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"-","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1451146","runsScored":0,"ballFaced":0,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"-","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1392796","runsScored":0,"ballFaced":1,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"c †Vinay Kedia b Lalit","catches":[],"stumping":[],"runout":[],"participatedRunout":[]}],"__v":0}
```

I want to sum the runsScored field of all objects inside score array. I know, I can achieve it using aggregation framework, but I am begineer in mongodb and does not have knowledge of many aggregation operators.

### >Solution :

To avoid `$unwind`

if you want to get the total for each document, you can use this aggregation stage:

```
db.collection.aggregate([
{
"$project": {
"sum": {
"$sum": "$score.runsScored"
}
}
}
])
```

The trick here is using `$score.runsScored`

it generates an array with all values, then you only have to `$sum`

these values.

Example here

The other way is using `$unwind`

and `$group`

like this. Note that in this example `_id`

is `null`

to sum all values in the collection, to get the total for each document you have to use `_id: $_id`

like this example