Mongodb是用Sum 和Where条件

Sum

按照条件求和

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db.aa.aggregate([                                             { $group: { _id: null, total: { $sum: "$value" } } }, //$value 指的是按照那一列来sum。比如 value是mongo的一列。那么此处应该是 $value                      { $sort: { total: -1 } }                    ])

 

 

Where条件

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db.myCollection.find( { $where: "this.credits == this.debits" } ); db.myCollection.find( { $where: "obj.credits == obj.debits" } );   db.myCollection.find( { $where: function() { return (this.credits == this.debits) } } ); db.myCollection.find( { $where: function() { return obj.credits == obj.debits; } } );