We propose a visual query language object query diagram (OQD) for object-oriented databases (OODBs). Unlike other approaches for OODBs, in which a class is used as a primitive entity for query specification, in OQD we specialize a class as a number of object sets, each of which is a domain of an attribute in the class. An object set is the primitive entity of designation in a query. OQD helps make queries simple by specifying a query without a complex path expression and give a better support for query optimization by removing the repetitive use of path expression and grouping the conditions which apply to a single class. Moreover, the basic structure of OQD derived from a schema graph can be easily extended to express a complex query because the entities of designation in a class, i.e. object sets, are isolated from each other.