has
The has keyword is used in TypeQL patterns to specify an owner for an attribute.
Syntax
The syntax of a has statement includes:
-
Subject — a concept variable representing a data instance
-
Predicate — the
haskeyword -
Object — an attribute represented by an optional attribute type with a concept variable or literal value
<data-instance> has <attribute>;Behavior
TypeQL statements with the has keyword can be used in data queries
to set a constraint of owning a particular attribute.
Usage in a match pattern
For this example, use a database with the IAM schema and sample data loaded.
To match a particular person by the value of the full-name it owns and return an email it owns:
match
$p isa person, has full-name "Kevin Morrison", has email $e;
fetch $e;See example output
{ "e": { "value": "kevin.morrison@typedb.com", "type": { "label": "email", "root": "attribute", "value_type": "string" } } }Usage in an insert pattern
For this example, use a database with the IAM schema and sample data loaded.
Let’s insert a new email for an existing person:
match
$p isa person, has full-name "Kevin Morrison";
insert
$p has email "m.kevin@gmail.com";By inserting ownership of an attribute that doesn’t exist in the database yet, we implicitly create such an attribute.
Usage in a delete pattern
For this example, use a database with the IAM schema and sample data loaded.
Let’s delete an ownership of the new email from the same person:
match
$p isa person, has full-name "Kevin Morrison", has email $e;
$e == "m.kevin@gmail.com";
delete
$p has $e;The above example deletes only ownership, but the email attribute itself is still in the database.
To delete the attribute, use the isa statement in a delete clause, for example,
see the isa page.