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copied!<p>There are several issues with your sample document and aggregation:</p> <ul> <li>the sample doc will not match your aggregation query because you are matching on <code>createdDate</code> field existing</li> <li>the <a href="http://docs.mongodb.org/manual/reference/aggregation/group/"><code>$group()</code> operator</a> works on a document level and needs an <code>_id</code> field to group by</li> <li>your <code>list</code> field is an embedded document, not an array</li> <li>aside from formatting, there is no obvious way to relate the sample values to the calculated result you are looking for</li> </ul> <p>Here is an adjusted example document with the <code>list</code> as an array as well as some unique values for each item that happen to add up to the <code>value</code> numbers you mentioned:</p> <pre><code>db.people.insert({ "ad" : "noc2", "createdDate" : ISODate(), "list" : [ { "id" : "p45", "date" : ISODate("2014-01-01T12:18:30.568Z"), "value3" : 21, "value1" : 77, "value2" : 489 }, { "id" : "p6", "date" : ISODate("2013-07-18T12:18:30.568Z"), "value3" : 20, "value1" : 20, "value2" : 7 }, { "id" : "4578", "date" : ISODate("2013-07-18T12:18:30.568Z"), "value3" : 21, "value1" : 300, "value2" : -319 } ] }) </code></pre> <p>You can now use the <a href="http://docs.mongodb.org/manual/reference/aggregation/unwind/"><code>$unwind</code> operator</a> to extract the matching subdocuments.</p> <p>It is unclear from the current question description what <code>$group</code> operation you are trying to achieve and whether you actually need <code>$group</code>.</p> <p>Here is an example using the Aggregation Framework to <a href="http://docs.mongodb.org/manual/reference/aggregation/add/"><code>$add</code></a> (total) the three values for each list item:</p> <pre><code>db.people.aggregate( // Find relevant docs (can use index if available) { $match: { createdDate: { $exists:true }, "ad":"noc2" }}, // Convert list array to stream of documents { $unwind: "$list" }, // Add (value1, value2, value3) for each list item { $project: { _id: "$list.id", value: { $add: [ "$list.value1", "$list.value2", "$list.value3"] } }} ); </code></pre> <p>Sample output:</p> <pre><code>{ "result" : [ { "_id" : "p45", "value" : 587 }, { "_id" : "p6", "value" : 47 }, { "_id" : "4578", "value" : 2 } ], "ok" : 1 } </code></pre> <p>Note that I've only aggregated using a single document for this example, and the output will be one result document for every item in the <code>list</code> array.</p> <p>In real usage you may want to add an additional aggregation step to <code>$group</code> by document <code>_id</code> or some other criteria, depending on the outcome you are trying to achieve.</p>

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