All integer types and their derivatives are accepted by the preprocessor. Even though some integer types do have Ada constraints, such as the types natural and positive, EQUEL does not check these constraints, either during preprocessing or at runtime. An integer constant is treated as an EQUEL constant value and cannot be the target of a Ingres assignment.

The type boolean is handled as a special type of integer. In Ada, the boolean type is defined as an enumerated type with enumerated literals false and true. EQUEL treats the boolean type as an enumerated type and generates the correct code in order to use this type to interact with a Ingres integer. Enumerated types are described in more detail later.