  Currently two query languages are defined as standards for the Virtual
Observatory (VO). Astronomical Data Query Language (ADQL) is used for catalog
data query and Simple Image Access Protocol (SIAP) is for image data query. As
a result, when we query each data service, we need to know in advance which
language is supported and then construct a query language accordingly. The
construct of SIAP is simple, but they have a limited capability. For example,
there is no way to specify multiple regions in one query, and it is difficult
to specify complex query conditions. In this paper, we propose a unified query
language for any kind of astronomical database on the basis of SQL99. SQL is a
query language optimized for a table data, so to apply the SQL to the image and
spectrum data set, the data structure need to be mapped to a table like
structure. We present specification of this query language and an example of
the architecture for the database system.
