How to make a "JOIN" in two Colections in Mongodb?

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6

I know Mongodb doesn’t have Ner Join, but I really need to filter the data from a Collection by reference to its _id in another Collection.

I need to display only the projects of a particular user.

No question of restructuring the base.

Collections:

usuarios: { _id: ObjectId("..."), nome: "usuario", ... }

projects:

{ _id: ObjectId("..."), nome: "projeto1", ...}

users:

{ _id: ObjectId("..."), idProjeto, idUsuario }

In short, I want to pass the _id user and he bring me all his projects without changing the structure above. It is possible?

mongodb nosql
  • 1

    You want to do it inside the Mongo Shell?

  • Whatever. I wonder if there’s a way out.

  • 1

    It exists, but it involves a programming language. Mongodb, as the answer given, does not have native support for joins. You who have to make your application read the dependent data.

  • You have the code of some solution with php for me to understand?

  • 1

    http://www.sitepoint.com/modeling-data-relationships-in-mongodb/

2 answers

7


Mongodb can’t stand it joins.

Unfortunately its structure does not match the functioning of Mongodb.

Mongodb is a non-relational database, you must centralize the data of each query in the same document.

The data from Collection usuariosProjetos should be part of Collection usuarios.

  • 1

    Well, there is no concept of "table" in Mongodb because it is a database without schema. The schema is defined in the application.

  • Yes, I changed the terms, I meant Collection

  • Now it’s okay. + 1.

2

Adding that from its version 3.4, mongodb brings the $lookup operator, which allows uniting records of two collections, from some common value between the two. But it’s just that. Complex joins like in relational database, forget about.

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