{ "_id" : ObjectId("5cd8609db20663a19e2c362c"), "2017" : { "JAN" : [ { "SYMBOL" : "20MICRONS", "SERIES" : "EQ", "OPEN" : "33.4", "HIGH" : "34.3", "LOW" : "33", }, { "SYMBOL" : "3IINFOTECH", "SERIES" : "EQ", "OPEN" : "5.8", "HIGH" : "5.8", "LOW" : "5.55", }, { "SYMBOL" : "3MINDIA", "SERIES" : "EQ", "OPEN" : "11199.9", "HIGH" : "11233", "LOW" : "10861", } ] } }
你可以用 $size
$size
db.collection.aggregate([ { "$project": { "totalJan": { "$size": "$2017.JAN" } } } ])
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