$project ## **創建幾個文檔** ~~~ (new cheshi())->goCheck('edit'); db.accounts.insertMany([ {name:{firstName:"alice",lastName:"wong"}, balance:50}, {name:{firstName:"bob",lastName:"yang"}, balance:20} ]) ~~~ ## **進行投影** ### **案例1：** ~~~ db.accounts.aggregate([ { $project:{ _id:0, balance:1, clientName:"$name.firstName" } } ]) ~~~ ### **返回案例** ``` { "balance" : 50, "clientName" : "alice" } { "balance" : 20, "clientName" : "bob" } ``` ## **案例2:** ~~~ db.accounts.aggregate([ { $project:{ _id:0, balance:1, nameArray:["$name.firstName","$name.middlename","$name.lastName"] } } ]) ~~~