Lesson 4: Writing data

Insert queries are used to insert data. They comprise either an insert clause only, or a match clause and an insert clause. Insert queries are run using a data session and write transaction.

insert
# insert clause

match
# match clause
insert
# insert clause

All attributes are multivalued, allowing an entity or relation to own any number of attributes of the same type, as long as they each have different values.

An Insert query without a match clause inserts data once. An Insert query with a match clause inserts data multiple times, once for each match found.

A polymorphic insert can be performed by using a polymorphic pattern in the match clause of an Insert query.

When inserting a relation, the roles can be omitted if they can be inferred unambiguously.

Delete queries are used to delete data. They comprise a match clause and a delete clause. Delete queries are run using a data session and write transaction.

match
# match clause
delete
# delete clause

Delete queries delete data per statement.

A has statement is used to delete an entity or relation’s attribute.

$entity has $deleted-attribute;

An isa statement is used to delete an entity or relation.

$deleted-entity isa entity-type;

When deleting a roleplayer in a relation, the relation must also be deleted manually if required. A relation is only deleted automatically if all of its roleplayers are deleted.

Update queries are used to update data. They comprise a match clause, a delete clause, and an insert clause. Update queries are run using a data session and write transaction.

match
# match clause
delete
# delete clause
insert
# insert clause

All inserted data is validated against the schema.

Inserting data that does not conform to the schema will cause an exception to be thrown.

An exception will also be thrown if deleting or updating data leads to an invalid state.