# Addressing


## Format

The SQL Server Transport address has the following canonical form:

```
table@[schema]@[catalog]
```

The meaning of the parts is the following:

 * `table` is an unquoted delimited identifier without the surrounding square brackets. Whitespace and special characters are allowed and are not escaped, e.g. `my table` and `my]table` are legal values. The identifier is quoted automatically by SQL Server transport when executing the SQL statements. `@` is a separator between the table and schema parts and thus is not a valid character.
 * `schema` is either an unquoted delimited identifier without the surrounding square brackets or a standard bracket-delimited identifier. In the second form, it is always surrounded by brackets, and any right brackets (`]`) inside are escaped, e.g. `[my]]schema]`. `@` is only allowed in the bracket-delimited form; otherwise, it is treated as a separator.
 * `catalog` has the same syntax as `schema`.



## Resolution

The address is resolved into a fully-qualified table name that includes the table name, its schema, and catalog. In the address, the table name is the only mandatory part. An address containing only a table name is a valid address, e.g. `MyTable`.


### Schema

The SQL Server transport needs to know what schema to use for a queue table when sending messages. The following API can be used to specify the schema for an endpoint when [routing](/nservicebus/messaging/routing.md) is used to find a destination queue table for a message:

<!-- snippet: sqlserver-multischema-config-for-endpoint -->

```cs
var routing = endpointConfiguration.UseTransport(new SqlServerTransport("connectionString"));

routing.RouteToEndpoint(typeof(MyMessage), "MyEndpoint");
routing.UseSchemaForEndpoint(endpointName: "MyEndpoint", schema: "my_schema");
```

<!-- endsnippet -->

There are several cases when routing is not used and the transport needs specific configuration to find out the schema for a queue table:

  - [Error queue](/nservicebus/recoverability/configure-error-handling.md#configure-the-error-queue-address)
  - [Audit queue](/nservicebus/operations/auditing.md#configuring-auditing)
  - ServiceControl plugin queues
    - [Heartbeats plugin](/monitoring/heartbeats/install-plugin.md)
    - [Custom Checks plugin](/monitoring/custom-checks/install-plugin.md)
  - [Overriding the default routing mechanism](/nservicebus/messaging/send-a-message.md#overriding-the-default-routing)
  - Replies to endpoints using SQL Server transport Version 2 and below

Use the following API to configure the schema for a queue:

<!-- snippet: sqlserver-multischema-config-for-queue -->

```cs
var transport = new SqlServerTransport("connectionString");

transport.SchemaAndCatalog.UseSchemaForQueue(queueName: "myqueue", schema: "my_schema");
transport.SchemaAndCatalog.UseSchemaForQueue(queueName: "myerror", schema: "sc");
```

<!-- endsnippet -->

The configuration above is applicable when sending to a queue or when a queue is passed in the configuration:

<!-- snippet: sqlserver-multischema-config-for-queue-send -->

```cs
await messageSession.Send("myqueue", new MyMessage());
```

<!-- endsnippet -->

<!-- snippet: sqlserver-multischema-config-for-queue-error -->

```cs
endpointConfiguration.SendFailedMessagesTo("myerror");
```

<!-- endsnippet -->

The entire algorithm for calculating the schema is the following:

 * If the schema is configured for a given queue via `UseSchemaForQueue`, the configured value is used.
 * If [logical routing](/nservicebus/messaging/routing.md#command-routing) is used and schema is configured for a given endpoint via `UseSchemaForEndpoint`, the configured schema is used.
 * If destination address contains a schema, the schema from address is used.
 * If default schema is configured via `DefaultSchema`, the configured value is used.
 * Otherwise, `dbo` is used as a default schema.



### Catalog


The SQL Server transport reads the default catalog from the `Initial catalog` or `Database` properties of the connection string. The following API can be used to override the default catalog for an endpoint when [routing](/nservicebus/messaging/routing.md) is used to find a destination queue table for a message:

<!-- snippet: sqlserver-multicatalog-config-for-endpoint -->

```cs
var routing = endpointConfiguration.UseTransport(new SqlServerTransport("connectionString"));

routing.RouteToEndpoint(typeof(MyMessage), "MyEndpoint");
routing.UseCatalogForEndpoint(endpointName: "MyEndpoint", catalog: "MyCatalog");
```

<!-- endsnippet -->

There are several cases when routing is not used and the transport needs specific configuration to find out the catalog for a queue table:

 * [Error queue](/nservicebus/recoverability/configure-error-handling.md#configure-the-error-queue-address)
 * [Audit queue](/nservicebus/operations/auditing.md#configuring-auditing)
 * [ServiceControl queue](/monitoring/heartbeats/install-plugin.md)
 * [Overriding the default routing mechanism](/nservicebus/messaging/send-a-message.md#overriding-the-default-routing)
 * Replies to endpoints using SQL Server transport version 2 and earlier

Use the following API to configure the schema for a queue:

<!-- snippet: sqlserver-multicatalog-config-for-queue -->

```cs
var transport = new SqlServerTransport("connectionString");

transport.SchemaAndCatalog.UseCatalogForQueue(queueName: "myqueue", catalog: "MyCatalog");
transport.SchemaAndCatalog.UseCatalogForQueue(queueName: "myerror", catalog: "ServiceControl");
```

<!-- endsnippet -->

The configuration above is applicable when sending to a queue or when a queue is passed in the configuration:

<!-- snippet: sqlserver-multicatalog-config-for-queue-send -->

```cs
await messageSession.Send("myqueue", new MyMessage());
```

<!-- endsnippet -->

<!-- snippet: sqlserver-multicatalog-config-for-queue-error -->

```cs
endpointConfiguration.SendFailedMessagesTo("myerror");
```

<!-- endsnippet -->

The entire algorithm for calculating the catalog is the following:

 * If the catalog is configured for a given queue via `UseCatalogForQueue`, the configured value is used.
 * If [logical routing](/nservicebus/messaging/routing.md#command-routing) is used and the catalog is configured for a given endpoint via `UseCatalogForEndpoint`, the configured value is used.
 * If the destination address contains a catalog, the catalog from the address is used.
 * Otherwise the catalog configured as `Initial catalog` or `Database` in the connection string is used.