Selecting a Specific Actor
Query By Id
Every subject in Fluree has a unique _id. This
_id is a long integer (a large number), and it is automatically generated when that subject is created. It will never change, and it can never be changed.
You can use this id to query one specific subject.
For example, if you knew an actor's _id, you could select them using "from": that_id.
Query By Unique Two-Tuple
An easier way to select a single subject is to specify any unique predicate and that predicate's object (value).
For example, in our movie ledger, the
actor/name predicate is unique. We can select the
actor Angelina Jolie with the following query:
"from": ["actor/name", "Angelina Jolie"]
We have to use a unique predicate for this purpose. If we want to select Angelina Jolie, and we specified her gender, then that wouldn't allow us to uniquely identify her.
If you weren't sure whether a predicate was unique, you could query it using:
"from": ["_predicate/name", "actor/name"]
Or, you could select all predicates: