如何从 mongodb 聚合管道中获取唯一值

Question

我当前的mongodb聚合管道输出是

[
    {
        "CustomerID":"E001",
        "CustomerName":"Suresh",
        "CustomerPhone":"919889902----",        
    },
    {
        "CustomerID":"E001",
        "CustomerName":"Suresh",
        "CustomerPhone":"919889902----",        
    },
    {
        "CustomerID":"E002",
        "CustomerName":"Ramesh",
        "CustomerPhone":"919889902----",        
    },
    {
        "CustomerID":"E003",
        "CustomerName":"Kishore",
        "CustomerPhone":"919889902----",        
    },
    {
        "CustomerID":"E002",
        "CustomerName":"Ramesh",
        "CustomerPhone":"919889902----",        
    },
    {
        "CustomerID":"E001",
        "CustomerName":"Suresh",
        "CustomerPhone":"919889902----",        
    }
];

根据CustomerID

，实际响应应该是唯一的

[
    {
        "CustomerID":"E001",
        "CustomerName":"Suresh",
        "CustomerPhone":"919889902----",        
    },
    {
        "CustomerID":"E002",
        "CustomerName":"Ramesh",
        "CustomerPhone":"919889902----",        
    },
    {
        "CustomerID":"E003",
        "CustomerName":"Kishore",
        "CustomerPhone":"919889902----",        
    }
];

我不知道使用什么运算符从聚合管道中获取唯一值。

我使用 $project, $sort 来投影响应，使用 $skip 和 $limit 来进行分页

Answer 1

按你想要的值分组：

db.collection.aggregate([
   {
     $group:{
       _id: "$CustomerID",
       CustomerId: {$first:"$CustomerID"},
       CustomerName: {$first: "$CustomerName"},
       CustomerPhone: {$first: "$CustomerPhone"}
    }
  }
]);

我假设同一客户 ID 的姓名和电话相同，否则将 $first 替换为 $addToSet 以获取所有姓名和电话