MongoDB的SELECT COUNT

Question

我有以下的數據庫

{"userName":"John Smith", "followers":8075,"body":"my text 1","confirmed":"no"} 
{"userName":"james Bond", "followers":819, "body":"my text 2", "confirmed":"yes"} 
{"userName":"Julia Roberts","followers":3882,"body":"my text 3","confirmed":"yes"} 
{"userName":"Jamal David","followers":6531, "body":"my text 4","confirmed":"yes"} 
{"userName":"jane fonda","followers":3941, "body":"my text 5","confirmed":"no"} 

我需要計數的追隨者的名字開始與JA的數量（不區分大小寫）

我試圖做到這一點，但這個選擇給了我所有的匹配線。

db.collections.find({ $and:[{followers: { $gte: 0 } }, {"userName" : {$regex :/^Ja/i}} ]}) 

而這僅僅給出匹配的行

db.collections.find({ $and:[{followers: { $gte: 0 } }, {"userName" : {$regex :/^Ja/i}} ]}).count() 

我怎樣才能提取的追隨者對匹配的行（詹姆斯，賈馬爾，簡）數量的總數是多少？

Answer 1

試試這個：

db.collections.aggregate([{ 
$match:{"userName":{$regex :/^Ja/i}} 
}, 
{$group:{ 
_id:null, 
followers: {$sum: "$followers"} 
}}])