Source: https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/data-types/boolean-type/
Documentation version: v5.3.2

# Boolean types

The boolean type is declared with the `BOOL` or `BOOLEAN` keyword and can be set to the following values: `TRUE`, `FALSE`, and `UNKNOWN` (equals `NULL`, indicating the unknown truth value).

## Declaration example

````
'''
CREATE GRAPH TYPE IF NOT EXISTS person AS  
    { NODE Person 
        ( { 
            id INT64 PRIMARY KEY,  
            is_adult BOOL DEFAULT TRUE,  
            name STRING DEFAULT 'John Doe',  
            hobbies LIST<STRING> DEFAULT ['reading', 'swimming'], 
            birthday DATE DEFAULT DATE('1990-01-01') 
        } ) 
    }
'''

````

In the preceding example, the property `is_adult` is of the boolean type (`BOOL`) with a default value of `TRUE`.

## Predicates

A predicate is a logical expression for filtering data in queries. It specifies a condition that evaluates to a boolean value. The following predicates are supported in GQL:

- [Comparison predicate](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/fe/predicates/comparison/)
- [EXISTS predicate](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/fe/predicates/exists/)
- [Null predicate](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/fe/predicates/null/)
- [Labeled predicate](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/fe/predicates/labeled/)
- [ALL_DIFFERENT predicate](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/fe/predicates/all_different/)
- [SAME predicate](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/fe/predicates/same/)