Based on OLE DB, the distributed query technology for SQL Server 7.0 enables queries to heterogeneous data sources. Any data source supported by ODBC/OLE can participate in a distributed query. For example, an international company has eight regional offices, each using a different database product to store sales data (Oracle, Microsoft Access, Microsoft Excel, SQL Server, and so on). The sales manager uses distributed queries to read the data from each data source and prepare a quarterly report showing the sales, salary, and commission results for the last three years.
SQL Server allows a single SELECT statement to be issued to databases to the data sources, tapping into all the power of SQL, including heterogeneous joins and subqueries. If an application does require access to distributed data, but the use of a particular piece of data is infrequent, distributed queries may be a better choice than replication.