# Example: Virtual Databases

A DAH has three child servers:

- server 0 has a database of dog information, called `dogs`.

- server 1 has:

  - a database of cat information, called `cats`.
  - a database of parrot information, called `parrots`.

- server 2 has a database of flower information, called `flowers`.

## Configuration

The following DAH VDB configuration queries all information about pets:

    [VDB0]
    Name=pets
    MapsTo=0:dogs,1:cats,1:parrots
    Type=combinator

In this example, note that:

- You do not have to reference all child servers in the `MapsTo` parameter.

- You can reference the same child server multiple times.

## Query

When DAH receives a query with `DatabaseMatch` set to `pets`, DAH sends:

- the query with `DatabaseMatch` set to `dogs` to server 0.

- the query with `DatabaseMatch` set to `cats+parrots` to server 1.

  TIP: There are other advanced distribution options for VDBs, such as multi-stage querying. For more information, refer to the DAH Reference.

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