如何使用mongodb使用特定键加入多个集合？

Posted 2023-01-14

我有3张桌子考虑1。用户表用户名，电子邮件，用户ID，对象ID2。角色表对象编号，角色编号，角色名称3。用户角色表对象ID，角色ID，用户ID

我需要使用猫鼬的用户死亡用户名，电子邮件，用户名，角色名需要解决方案

答案

db.users.aggregate([

    // Join with user_info table
    
        $lookup:
            from: "user_role",      
            localField: "userId",   
            foreignField: "userId", 
            as: "user_role"         
        
    ,
       $unwind:"$user_role" ,     // $unwind used for getting data in object or for one record only

    // Join with user_role table
    
        $lookup:
            from: "role", 
            localField: "roleId", 
            foreignField: "roleId",
            as: "user_role"
        
    ,
       $unwind:"$role" ,

    // define some conditions here 
    
        $match:
            $and:["userid" :1]
        
    ,

    // define which fields are you want to fetch
       
        $project:
            _id : 1,
            email : 1,
            userName : 1,
            userPhone : "$user_info.phone",
            role : "$user_role.role",
         
    
])