Increasingly common, innovative business projects have a need to integrate various databases to extract information. Those of us, who were in the industry for long enough, have seen it all. Relational and non-relational databases, CSV or Excel files. Most probably, those sources were not even designed to be used together. Traditionally, some kind of ETL project had to be created. It would load the data into “stage” tables, apply necessary transformations (like data type unification), and finally load the data somewhere. Time of the project would be measured in days or weeks rather than hours. Moreover, qualified staff is required, with knowledge about all source systems and the destination system. Using data virtualization tool like Querona, time-to-solution can be cut down to hours/minutes for one person. This article will show you step by step how to do it.


We will describe how to integrate 3 data sources: SQL Server, Oracle and MongoDB. First, we will import metadata from source systems, then we will show how to join data from those disparate sources using T-SQL and access data using a single data interface.

Metadata Import

To work with external data sources we need to import metadata from those sources. Let’s use Oracle Northwind database and see how to do it in practice using Querona. Step 1. Go to the Databases panel, click Add Database and fill necessary fields. Select “Oracle” from the list of databases supported by Querona. We support over 100 data source types.
Creating oracle connection
Step 2. Definition of new connection requires us to tell Querona how to reach the Oracle server. In our case, TNS Alias was provided alongside login and password. To make sure that connection can be established, click “Test Connection” button.
Step 3. Select which tables are we interested in and click “Create” button. For this example, only Northwind database will be useful, so that was our selection.
Virtual Database “OracleDatabase” was created and metadata for this Virtual Database was imported from Oracle’s Northwind database into Querona. Keep in mind that no data was loaded from Oracle.
That is all that was required to connect a data source to Querona and import metadata. Import metadata process for 2 another sources is very similar, so for the sake of brevity, we will skip it.
Now we can start executing queries against Querona using standard T-SQL, known from Microsoft SQL Server.

Joining data from all three sources

Now we will show you how easy it is to work with data from those disparate sources. Because Querona emulates SQL Server protocol (called TDS – tabular data stream), we can connect to it using SQL Server Managment Studio . Our virtual databases are displayed as if they were standard SQL Server databases.
Now we can just query all of them at once:
Querona will load data from source systems and join them according to our needs. All the differences of source systems (like different data types, storage models) are accounted for and transparently resolved.


Data virtualization is a rising technology that dramatically reduces time and cost of integration processes. We have shown how straightforward it is to integrate different data sources, one of which (MongoDb) was not even relational. Hopefully, we convinced you that integrating data from multiple databases does not have to be a lengthy and troublesome process. Instead, using Querona, you can make it easy, fast and flexible by effectively removing the need for ETL processes.