Question

我试图在我的Mongo查询中创建计算状态字段（状态：已创建，付款已收到，已发货，已收到，已完成）。

db.orders.aggregate( [
   { $project: { status: {
      $cond: { if: { $ne: ["$feedback", null] }, 
      then: 'finished', else: {
         $cond: { if: { $ne: ["$received", null] }, 
         then: 'received', else: {
            $cond: { if: { $ne: ["$shipped", null] }, 
            then: 'shipped', else: {
               $cond: { if: { $ne: ["$payment", null] }, 
                  then: 'payment received', else: 'created' }
            } }
         } } 
      } }
   } } },
   { $match: {  } }
] )

示例数据：

{
    "_id" : "xxxxxx0",
    "payment" : ISODate("2016-02-03T10:45:00.011Z"),
    "shipped" : ISODate("2016-02-03T11:55:00.011Z"),
    "received" : ISODate("2016-02-03T12:45:00.011Z"),
    "feedback" : ISODate("2016-02-03T14:34:00.011Z")
},
{
    "_id" : "xxxxxx1",
    "payment" : ISODate("2016-02-03T10:45:00.011Z"),
    "shipped" : ISODate("2016-02-03T11:55:00.011Z"),
    "received" : ISODate("2016-02-03T12:45:00.011Z")
},
{
    "_id" : "xxxxxx2",
    "payment" : ISODate("2016-02-03T10:45:00.011Z"),
    "shipped" : ISODate("2016-02-03T11:55:00.011Z")
},
{
    "_id" : "xxxxxx3",
    "payment" : ISODate("2016-02-03T10:45:00.011Z")
},
{
    "_id" : "xxxxxx4"
}

出于某种原因，我的所有结果都显示为“已完成”，我是否使用了$ cond错误？它是否支持嵌套的$ cond？

Answer 1

如果要检查字段是否存在，则不能使用$ eq null，它将始终返回true 使用$ gt可以做到这一点。您可以在此处查看完整说明（https://docs.mongodb.com/manual/reference/bson-types/#bson-types-comparison-order）

(<% %>)

$ cond聚合中的嵌套条件

1 个答案: