---
title: Multi-nested database connections example
---

The `OrmLiteConnectionFactory` class supports registering multiple named connections allows you to define all your 
db connections when registering it in your IOC, that can be accessed later using its registered name.

## Primary DB & Multi Shard DB Example

A popular way of scaling RDBMS's is to create a Master / Shard setup where datasets for queries that span entire system
are kept in the master database, whilst context-specific related data can be kept together in an isolated shard.
This feature makes it trivial to maintain multiple separate db shards with a master database in a different RDBMS.

Here's an (entire source code) sample of the code needed to define, and populate a Master/Shard setup.
Sqlite can create DB shards on the fly so only the blank SqlServer master database needed to be created out-of-band:

### Sharding 1000 Robots into 10 Sqlite DB shards

```csharp
public class MasterRecord {
    public Guid Id { get; set; }
    public int RobotId { get; set; }
    public string RobotName { get; set; }
    public DateTime? LastActivated { get; set; }
}

public class Robot {
    public int Id { get; set; }
    public string Name { get; set; }
    public bool IsActivated { get; set; }
    public long CellCount { get; set; }
    public DateTime CreatedDate { get; set; }
}

const int NoOfShards = 10;
const int NoOfRobots = 1000;

var dbFactory = new OrmLiteConnectionFactory(
    "Data Source=host;Initial Catalog=RobotsMaster;Integrated Security=SSPI",  //Connection String
    SqlServerDialect.Provider); 

dbFactory.Run(db => db.CreateTable<MasterRecord>(overwrite:false));

NoOfShards.Times(i => {
    var namedShard = "robots-shard" + i;
    dbFactory.RegisterConnection(namedShard, 
        $"~/App_Data/{shardId}.sqlite".MapAbsolutePath(),                //Connection String
        SqliteDialect.Provider);
	
	dbFactory.OpenDbConnection(namedShard).Run(db => db.CreateTable<Robot>(overwrite:false));
});

var newRobots = NoOfRobots.Times(i => //Create 1000 Robots
    new Robot { Id=i, Name="R2D"+i, CreatedDate=DateTime.UtcNow, CellCount=DateTime.Now.ToUnixTimeMs() % 100000 });

foreach (var newRobot in newRobots) 
{
    using (IDbConnection db = dbFactory.OpenDbConnection()) //Open Connection to Master DB 
    {
        db.Insert(new MasterRecord { Id = Guid.NewGuid(), RobotId = newRobot.Id, RobotName = newRobot.Name });
        using (IDbConnection robotShard = dbFactory.OpenDbConnection("robots-shard"+newRobot.Id % NoOfShards)) //Shard
        {
            robotShard.Insert(newRobot);
        }
    }
}
```

Using the [SQLite Manager](https://addons.mozilla.org/en-US/firefox/addon/sqlite-manager/?src=search) Firefox extension
we can peek at one of the created shards to see 100 Robots in each shard. This is the dump of `robots-shard0.sqlite`:

![Data dump of Robot Shard #1](/img/pages/ormlite/robots-shard0.sqlite.jpg)

As expected each shard has every 10th robot inside.