使用mongodb搜索多個集合

Question

我想檢查多個文件上是否存在特定數據。

例如，我想檢查用戶集合中是否存在電子郵件，如果客戶集合中確實存在電子郵件，那么我想獲取數據。

我已經在下面的查詢中嘗試過，但是由於僅檢查一個集合而失敗。

db.t_usermasters.aggregate([
{
    $match: {
        "email" : "test@test.com"
    }
},{
    $lookup: {
        from: "t_customermasters",
        localField: "email",
        foreignField: "email",
        as: "UserDetails"    
  }
}
]).pretty();

Answer 1

試試這個代碼：

db.t_usermasters.aggregate([
{
    $match: {
        "email" : "test@test.com"
    }
},{
    $lookup: {
        from: "t_customermasters",
        localField: "email",
        foreignField: "email",
        as: "UserDetails"    
  }
}, {
    $match: { 
    UserDetails: { $exists: true, $not: {$size: 0} } 
 } 
}

]).pretty();

Answer 2

您實際上需要在t_customermasters進行查找，並通過使用空數組進行調節來進行下推

db.t_usermasters.aggregate([
        {
            $match: {
                "email" : "test@test.com"
            }
        },
        {
            $lookup: {
                from: "t_customermasters",
                localField:"email",
                foreignField:"email",
                as: "UserDetails"    
          }
        },
        {
            $project:{
                _id:true,
                email:true,
                emailExistInBoth:{
                    $cond:{
                        if:{
                            $eq:[{$size:"$UserDetails"},0]
                        },
                        then:false,
                        else:true
                    }
                }
            }
        },
        {
            $match:{
                "emailExistInBoth":true
            }
        }
        ]).pretty();

Answer 3

if(db.t_usermasters.count({email: 'test@test.com'}) 
     && db.t_customermasters.count({email: 'test@test.com'})) {

   /* fetch your data here
      you can associate these two collections by using a customerId field in your 
      usermasters collection and then populate it ('customerId') 
      while fetching the data from usermasters collection */
}