Returning data from collection columns 

How to retrieve data from a collection.

Collections do not differ from other columns in retrieval. To query for a subset of the collection, a secondary index for the collection must be created.

Procedure

  • Retrieve teams for a particular cyclist id from the set.
     SELECT lastname, teams FROM cycling.cyclist_career_teams WHERE id = 5b6962dd-3f90-4c93-8f61-eabfa4a803e2;
    To query a table containing a collection, the database retrieves the collection in its entirety. Keep collections small enough to be manageable because the collection store in memory. Alternatively, construct a data model to replace a collection if it must accommodate large amounts of data.

    The database returns results in an order based on elements types in the collection. For example, a set of text elements is returned in alphabetical order. If you want elements of the collection returned in insertion order, use a list.



  • Retrieve events stored in a list from the upcoming calendar for a particular year and month.
     SELECT * FROM cycling.upcoming_calendar WHERE year=2015 AND month=06;


    Note: The order is not alphabetical, but rather in the order of insertion.
  • Retrieve teams for a particular cyclist id from the map.
     SELECT lastname, firstname, teams FROM cycling.cyclist_teams WHERE id=5b6962dd-3f90-4c93-8f61-eabfa4a803e2;
    The order of the map output depends on the key type of the map. In this case, the key is an integer type.