How to retrieve only the labels?

Question

Is there a query to retrieve only the labels for nodes and edges from a graph in a database? I know a query to retrieve the data information for nodes and edges from a graph, but it retrieves all the information. I'm wondering if there is a query to retrieve only the label information for nodes and edges.

Answer 1

This command will show you all the labels for all graphs under your database:

SELECT * FROM ag_catalog.ag_label; 

Answer 2

If you want to retrieve only the labels with cypher, you can execute the following command:

-- showing the vertex labels only
SELECT * FROM cypher('graph_name', $$
MATCH (v)
RETURN label(v)
$$) AS (vertex_label agtype);

-- showing the edge labels only
SELECT * FROM cypher('graph_name', $$
MATCH ()-[e]-()
RETURN label(e)
$$) AS (edge_label agtype);

And you can also retrieve it like everyone stated here:

SELECT * FROM ag_catalog.ag_label;

Answer 3

Let's suppose we have a Vertex With a single label v and properties name. We can use the query

Select * from cypher('demo' ,$$ Match(v:p) Return v $$ ) as (vertex agtype);

to return all the labels and their properties e.g

vertex
{"id": 9288674321451649, "label": "p", "properties": {"name": "John"}}::vertex

Now when we only need the labels we run the query:

Select * from cypher('demo' ,$$ Match(v:p) Return labels(v) $$  ) as (vertex agtype);

to get the following:

vertex
"p"

And you can also do:

SELECT * FROM ag_catalog.ag_label;