MongoDB投影整个子文档
我的收藏中有一大堆这样的文件MongoDB投影整个子文档,mongodb,mongodb-query,Mongodb,Mongodb Query,我的收藏中有一大堆这样的文件 { "success": true, "timestamp": 1519296206, "base": "EUR", "date": "2018-07-04", "rates": { "AUD": 1.566015, "CAD": 1.560132, "CHF": 1.154727, "CNY": 7.827874, "GBP": 0.882047, "JPY": 132.360679, "USD": 1.23
{
"success": true,
"timestamp": 1519296206,
"base": "EUR",
"date": "2018-07-04",
"rates": {
"AUD": 1.566015,
"CAD": 1.560132,
"CHF": 1.154727,
"CNY": 7.827874,
"GBP": 0.882047,
"JPY": 132.360679,
"USD": 1.23396,
}
}
我只想得到date
和整个rates
子文档,如下所示。我知道我可以将费率.AUD
,费率.CAD
等添加到投影中,但这会使投影非常大,无法阅读,并且很难维护,因为将来可能会添加一个新字段(或货币)
{
"date": "2018-07-04",
"rates": {
"AUD": 1.566015,
"CAD": 1.560132,
"CHF": 1.154727,
"CNY": 7.827874,
"GBP": 0.882047,
"JPY": 132.360679,
"USD": 1.23396,
}
}
有没有类似于上面描述的{date:1,“rates.*.1}
的投影
db.col.aggregate([ {
$project: {
date: 1,
rates: 1
}
}])
使用
db.collection.find()