Query to join multiple collections

[Adi]

Hi 

i'm working with a database and need to find a way to create a query to join multiple collections.

In the collections which need joining there are fields which contain arrays of pointers

Example:

userid: dh2892938d9

username: exampleuser

carparts:  array(

    array(

              collection-name: "name of another collection"

              id: "id of row in other collection"

     ), array(

              collection-name: "name of another collection"

              id: "id of row in other collection"

     ), array(

              collection-name: "name of another collection"

              id: "id of row in other collection"

     ),

)

There are also often pointers in the secondary collection pointing to another collection

At the moment I'm running multiple queries by following each pointer but it's a lot of connections. 

Is there a way of querying everything in one query using joins somehow?

Thanks for any help

Adi

[Kevin Adistambha]

Hi Adi

Is there a way of querying everything in one query using joins somehow?

MongoDB since version 3.2 provides the $lookup operator in the aggregation framework that does a left outer join of two collections.

Having said that, it looks like your MongoDB schema design was inherited from a relational database. Is this correct? Typical MongoDB schema design would embed subdocuments and denormalize the data, so that the application can find the most common case data it needs with a single find() query.

For more information about MongoDB schema design, please see:

• Data Model Examples and Patterns
• 6 Rules of Thumb for MongoDB Schema Design: Part 1

Best regards
Kevin

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