您将需要在应用程序代码中或在MongoDB 2.2中使用新的AggregationFramework来操纵嵌入式数组。
mongoShell中的示例聚合：
db.students.aggregate(
// Initial document match (uses index, if a suitable one is available)
{ $match: {
_id : 1
}},
// Expand the scores array into a stream of documents
{ $unwind: '$scores' },
// Filter to 'homework' scores
{ $match: {
'scores.type': 'homework'
}},
// Sort in descending order
{ $sort: {
'scores.score': -1
}}
)
样本输出：
{
"result" : [
{
"_id" : 1,
"name" : "Aurelia Menendez",
"scores" : {
"type" : "homework",
"score" : 71.76133439165544
}
},
{
"_id" : 1,
"name" : "Aurelia Menendez",
"scores" : {
"type" : "homework",
"score" : 34.85718117893772
}
}
],
"ok" : 1
}
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