Data definition language (DDL)

The Data definition language (DDL) in Kùzu defines the commands and statements that create, alter, and delete database objects. The schema provides a logical grouping of node and relationship tables that define the structure of the graph database.

Create (statement)

As a first step to creating your database, you need to define your node and directed relationships. In the property graph model, nodes and relationships have labels. In Kùzu, every node or relationship can have one label. The node and relationships and the predefined properties on them are defined through CREATE NODE TABLE and CREATE REL TABLE statements. The choice of using the term “table” over “label” is intentional and explained below.

Kùzu uses the term table rather than label because, like other GDBMSs, Kùzu is ultimately a relational system in the sense that it stores and processes sets of tuples, i.e., tables or relations.

In fact, Kùzu’s data model can be viewed as a structured property graph model, in which you tag your tables as “node” and “relationship” tables depending on their roles in your application data. Nodes are generally well-suited for representing entities, while relationships are used to represent the connections between these entities. Relationships are also the primary means to join nodes with each other to find paths and patterns in your graph database. So when you sketch out a mental map of your nodes/relationships, it is equivalent to defining your records as nodes or relationship tables.

During querying you can bind node records with syntax like (a:Person), and relationships with syntax like (..)-[e:Knows]->(...). Similar to table definitions in SQL, node and relationship tables have primary keys, a term that is defined in the context of tables: node tables explicitly define primary keys as one of their properties, while the primary keys of relationship tables are implicitly defined by the primary keys of their FROM and TO node records. Furthermore (similar to relational systems), properties can be thought of as equivalent to columns in a table, justifying our choice of using the term “table” in our design of the system.

Click on the card below to learn more about creatin node and relationship tables in Kùzu.

CREATE Create node and relationship tables

Alter

You can update the schema of a table using ALTER TABLE.

ALTER Update the schema of a node or relationship table

Drop

You can drop tables from the database with the DROP TABLE.

DROP Drop node or relationship table