As we saw, collection columns are a useful and versatile feature of CQL. In fact, we might suppose that collections would be a good way to model data we've modeled in other ways in previous chapters. For instance, why not model a user's status updates as a list of text values in the users table?
As it turns out, collection columns do have some limitations that circumscribe the cases in which they're the best solution. We'll explore the major limitations now.
The most powerful feature of CQL collections is the ability to write discrete values to a collection. It's possible to append a single value to a list, update a single key-value pair in a map, remove a specific value from a set, and so on.
At read time, however, there is no special support for reading discrete values. For instance, we might want to be able to do something like the following to read a specific element from a list column:
SELECT "shared_by"[2] FROM "user_status_updates...