NULL Value

Null indicates that a data value has not been provided. It is not the same as an empty string ("") or 0, as those represent specific values.

The two valid input formats for a null value are NULL and null.

Schema Definition

Any non-key vertex or edge attribute can be defined with the NULLABLE keyword, which allows it to store NULL values.

The following cannot be NULLABLE because they are used as key:

If an attribute is defined to be NULLABLE and DEFAULT is not specified, then its default value is NULL.

For modifying an existing schema, the same principles apply as in CREATE VERTEX or CREATE EDGE syntax.

Primitive types used as vertex or edge attributes can be set to NULL.
Collection types (LIST, SET, MAP) can be set to NULL as a whole, but NULL elements within a collection are not supported.

For MAP, neither keys nor values can be NULL.

A null value can be loaded into the database in three circumstances:

The input data source contains NULL values.
The loading job indicates via the underscore (_) that an attribute is to be skipped. In this case, if a default value has been specified, the default value is loaded. Otherwise, if the attribute is nullable, the null value is loaded. If neither of those conditions hold, then the default value for that attribute type (e.g., 0 for integer) is loaded.
The loading job explicitly specifies NULL for an attribute.

Attempting to load a null value into a non-nullable attribute causes a loading failure.

In both JSON and CSV output, the null value is represented as null.

See the PRINT statement section for more details.

The truth table below shows the results of AND and OR when NULL is involved.

x	y	x AND y	x OR y
TRUE	TRUE	TRUE	TRUE
TRUE	FALSE	FALSE	TRUE
TRUE	NULL	NULL	TRUE
FALSE	TRUE	FALSE	TRUE
FALSE	FALSE	FALSE	FALSE
FALSE	NULL	FALSE	NULL
NULL	TRUE	NULL	TRUE
NULL	FALSE	FALSE	NULL
NULL	NULL	NULL	NULL

x AND y

x OR y

TRUE

FALSE

TRUE

NULL

TRUE

FALSE

TRUE

FALSE

TRUE

FALSE

NULL

FALSE

NULL

TRUE

NULL

TRUE

NULL

FALSE

NULL