Question

如何找到有条件的数据？我需要该条件仅与dpt属性中的最后一个匹配。我需要检查上次departmentID说xyz

的位置

这是我的DB：

 {
        "_id" : ObjectId("56b08ceb19e01cd3240fc1ff"),
        "empCode" : "vss815",
        "firstName" : "ashu123",
        "lastName" : "kashyap",
        "status" : true,
        "dpt" : [ 
            {
                "departmentID" : ObjectId("56b0402a92b2a18116bf51de"),
                "effFrom" : ISODate("2016-02-02T11:03:07.972Z")
            }, 
            {
                "departmentID" : ObjectId("56b32c40e11ac0222034956c"),
                "effFrom" : ISODate("2016-02-04T10:48:04.406Z")
            }, 
            {
                "departmentID" : ObjectId("56b32c3ee11ac0222034956b"),
                "effFrom" : ISODate("2016-02-17T09:02:38.148Z")
            }
        ],

    }

我正在尝试的是：

  objMdlEmp.find({ 'dpt.departmentID':id } , {} , {'dpt.$' : 1})     
    .populate('dpt.departmentID')    
     .exec(function (err, result){         
        if(!err){
            callback(true , result);       
        }     
    });

但它从所有dpt数组中找到。

Answer 1

请尝试使用$unwind，$sort和$group来执行此操作：

objMdlEmp.aggregate([
    {$unwind: '$dpt'}, 
    // Sort the by effFrom
    {$sort: {'dpt. effFrom': -1}}, 
    // Group by effFrom, taking the first dept
    {$group: {
        _id: { effFrom: '$effFrom' }, 
        dpt: {$first: '$dpt'}
    }}
    // Shape back to the original style
    {$project: {_id: 1, dpt: 1}}
],
function(err, rets) {
    objMdlEmp.populate( rets, { "path": "dpt.departmentID" }, 
        function(err,results) {
         //
});

Mongoose仅在数组对象中查找最后一个数据

1 个答案: