Search on multiple collections in MongoDB

by

This answer is outdated. Since version 3.2, MongoDB has limited support for left outer joins with the $lookup aggregation operator

MongoDB does not do queries which span multiple collections – period. When you need to join data from multiple collections, you have to do it on the application level by doing multiple queries.

  1. Query collection A
  2. Get the secondary keys from the result and put them into an array
  3. Query collection B passing that array as the value of the $in-operator
  4. Join the results of both queries programmatically on the application layer

Having to do this should be rather the exception than the norm. When you frequently need to emulate JOINs like that, it either means that you are still thinking too relational when you design your database schema or that your data is simply not suited for the document-based storage concept of MongoDB.

More Related Contents:

  1. Retrieve only the queried element in an object array in MongoDB collection
  2. Update MongoDB field using value of another field
  3. Get names of all keys in the collection
  4. How to filter array in subdocument with MongoDB [duplicate]
  5. MongoDB: Combine data from multiple collections into one..how?
  6. Multiple join conditions using the $lookup operator
  7. Conditional $sum in MongoDB
  8. exclude fields in $lookup aggregation
  9. MongoDB aggregation comparison: group(), $group and MapReduce
  10. Add some kind of row number to a mongodb aggregate command / pipeline
  11. MongoDB group by array inner-elements
  12. Multiple Counts with single query in mongodb
  13. Mongo sort on a calculated condition
  14. MongoDB sort documents by array elements
  15. How to return array of string with mongodb aggregation
  16. How to return just the nested documents of an array from all documents
  17. MongoDB: Calculate dwell time between every status value change
  18. MongoDB: how to parse date in 3.6 mongoDb version?
  19. convert iso date to timestamp in mongo query
  20. Using $slice operator to get last element of array
  21. Mongodb aggregation $group, restrict length of array
  22. Get n-th element of an array in MongoDB
  23. Geospatial $near within current document field value
  24. How do I rename fields when performing search/projection in MongoDB?
  25. Mongodb aggregation pipeline how to limit a group push
  26. Mongodb concat int and string
  27. Mongodb, aggregate query with $lookup
  28. mongodb aggregate query isn’t returning proper sum on using $sum
  29. Return the last “true” value for each group
  30. MongoDB aggregate within daily grouping [duplicate]

Leave a Comment