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MongoDB university M101P HW5.4
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| db.zips.aggregate([ | |
| {$project: | |
| { | |
| fc: {$substr : ["$city",0,1]}, | |
| city:1,pop:1 | |
| } | |
| }, | |
| {$match:{fc:{$lte:"9",$gte:"0"}}} , | |
| { | |
| $group: { | |
| _id: null, | |
| allpop: { $sum: "$pop"} | |
| } | |
| } | |
| ]) |
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