# DROP VLABEL and DROP ELABEL Removes a vertex label or an edge label, and with `CASCADE` the rows in it. ## Synopsis

DROP VLABEL [ IF EXISTS ] label_name [, ... ] [ CASCADE | RESTRICT ]
DROP ELABEL [ IF EXISTS ] label_name [, ... ] [ CASCADE | RESTRICT ]

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## Description `DROP VLABEL` drops a vertex label and `DROP ELABEL` an edge label; each refuses the other kind. Dropping a label drops the table behind it, along with its id sequence, its indexes and its constraints. `RESTRICT`, which is the default, has two things to object to: - **Rows.** A label that still holds vertices or edges is refused with `cannot drop because it is not empty.` This is stricter than the dependency check PostgreSQL applies to a table, and it catches people out. - **Children.** A label with a child label is refused, and the message names the child. `CASCADE` overrides both. It drops a label whatever it holds, and: - dropping a **vertex** label deletes the edges attached to its vertices, whatever labels those edges have. The edge labels themselves survive. - dropping an **edge** label deletes only its own edges. The vertices they connected survive. The label is looked up in the graph named by `graph_path`; the name cannot be qualified. - The base labels `ag_vertex` and `ag_edge` cannot be dropped. - The table behind a label cannot be dropped on its own: `DROP TABLE` on it is refused and points you here. - To empty a graph without dropping its labels, use `MATCH (n) DETACH DELETE n` instead. ## Parameters IF EXISTS : Issue a notice instead of an error for a label that does not exist. Other names in the same statement are still dropped. label_name : Name of the label to drop. Several names may be given, separated by commas. CASCADE : Drop the label along with its rows and its child labels. For a vertex label, also drop the edges attached to its vertices. RESTRICT : Refuse if the label holds any rows or has a child label. This is the default. ## Examples The examples build their own graph, `tidygraph`, rather than using [the example dataset](../../get_started/example-dataset.md), and drop it at the end. ```cypher CREATE GRAPH tidygraph; SET graph_path = tidygraph; CREATE VLABEL film; CREATE VLABEL person; CREATE ELABEL directed; CREATE (:person {name: 'Denis Villeneuve'})-[:directed]->(:film {title: 'Arrival'}); CREATE VLABEL draft; ``` ### Drop an empty label ```cypher DROP VLABEL draft; ``` ``` DROP VLABEL ``` Nothing else is reported, because nothing else was affected. ### Drop a label that still holds vertices `film` has a vertex in it, so the default refuses: ```cypher DROP VLABEL film; ``` ``` ERROR: cannot drop film because it is not empty. ``` `CASCADE` takes the label, its vertex, and the `directed` edge that pointed at it: ```cypher DROP VLABEL film CASCADE; ``` ``` DROP VLABEL ``` ```cypher MATCH ()-[e:directed]->() RETURN count(e) AS directed_edges; ``` ``` directed_edges ---------------- 0 (1 row) ``` The edge is gone but its label is not. `directed` is still there, empty: ```psql \dGl tidygraph.dir* ``` ``` List of labels Graph | Name | Type | Owner -----------+----------+------+------- tidygraph | directed | edge | agens (1 row) ``` ### Drop a parent label ```cypher CREATE VLABEL work; CREATE VLABEL documentary INHERITS (work); DROP VLABEL work; ``` ``` ERROR: cannot drop vlabel work because other objects depend on it DETAIL: vlabel documentary depends on vlabel work HINT: Use DROP ... CASCADE to drop the dependent objects too. ``` `CASCADE` names the child it takes with it: ```cypher DROP VLABEL work CASCADE; ``` ``` NOTICE: drop cascades to vlabel documentary DROP VLABEL ``` ### Drop several labels, skipping the ones that are gone ```cypher CREATE VLABEL a; CREATE VLABEL b; DROP VLABEL IF EXISTS a, b, c; ``` ``` NOTICE: vlabel "c" does not exist, skipping DROP VLABEL ``` ### Refusals worth recognizing Each statement drops one kind of label: ```cypher DROP ELABEL person; ``` ``` ERROR: DROP ELABEL cannot DROP vertex label ``` The base labels stay: ```cypher DROP VLABEL ag_vertex; ``` ``` ERROR: DROP base vertex label is prohibited ``` And the table cannot be dropped out from under the label: ```sql DROP TABLE tidygraph.person; ``` ``` ERROR: cannot drop table tidygraph.person because vlabel person requires it HINT: You can drop vlabel person instead. ``` Finally, drop the graph the examples built: ```cypher DROP GRAPH tidygraph CASCADE; ``` ## Notes An edge whose endpoint vertex is deleted is deleted with it, both here and in `DETACH DELETE`. `start` and `end` are plain `graphid` columns rather than foreign keys. The graph write path does this, not a referential action on the table. ```{note} `cypher_allow_unsafe_ddl` switches off the kind check and the base-label check, so with it on `DROP ELABEL` will drop a vertex label and `ag_vertex` can be dropped. It exists to repair a graph whose catalog is already wrong. Leave it off otherwise. ``` ## Compatibility ### ISO/IEC 39075 (GQL) GQL has no statement that drops a label. Element types belong to a graph type, which is dropped whole by `` (§12.7), and dropping one does not delete any data. Graph types are tracked as planned in the [GQL conformance matrix](../../appendix/gql-conformance.md). ### PostgreSQL `DROP VLABEL` and `DROP ELABEL` correspond to `DROP TABLE`, and `IF EXISTS`, the name list and `CASCADE`/`RESTRICT` behave as they do there. One addition has no `DROP TABLE` counterpart. `DROP TABLE` does not care how many rows a table has; these statements refuse a label that is not empty unless you write `CASCADE`. And for a vertex label, `CASCADE` also deletes edges in *other* labels. Read `CASCADE` here as "and the graph data that depends on it", not only "and the dependent catalog objects". ## See also - [`CREATE VLABEL`](create-vlabel.md) - [`CREATE ELABEL`](create-elabel.md) - [`ALTER VLABEL` and `ALTER ELABEL`](alter-label.md) - [`DROP GRAPH`](drop-graph.md) - [Label inheritance](../../concepts/label-inheritance.md)