Abstract: An interval constraint database provides a uniform framework for handling spatial and non-spatial data. It is based on relational databases while supporting interval constraint data. In order to manage interval constraint data, an interval constraint database query language ISQL is proposed based on this model. ISQL provides the full query capabilities of SQL on the non-spatial part of the database while being tightly integrated with the spatial part. The syntax and semantics of ISQL is defined and an extension of SQL2 is proposed for the management of interval constraint data. Its specification and examples by queries are given by means of union and except, data insertion, deletion, update, etc. based on the interval constraint data model.Finally, the closure property for ISQL is discussed.