Materialize/doc/user/content/sql/create-source/sql-server.md

---

title: "CREATE SOURCE: SQL Server" description: "Connecting Materialize to a SQL Server database for Change Data Capture (CDC)." pagerank: 40 menu: main:

parent: 'create-source'
identifier: cs_sql-server
name: SQL Server
weight: 20

---

{{< private-preview />}}

{{% create-source/intro %}} Materialize supports SQL Server (2016+) as a real-time data source. To connect to a SQL Server database, you first need to tweak its configuration to enable Change Data Capture and SNAPSHOT transaction isolation for the database that you would like to replicate. Then create a connection in Materialize that specifies access and authentication parameters. {{% /create-source/intro %}}

Syntax

{{< diagram "create-source-sql-server.svg" >}}

with_options

{{< diagram "with-options-retain-history.svg" >}}

Field	Use
_srcname	The name for the source.
IF NOT EXISTS	Do nothing (except issuing a notice) if a source with the same name already exists. Default.
IN CLUSTER _clustername	The cluster to maintain this source.
CONNECTION _connectionname	The name of the SQL Server connection to use in the source. For details on creating connections, check the CREATE CONNECTION documentation page.
FOR ALL TABLES	Create subsources for all tables with CDC enabled in all schemas upstream.
FOR TABLES ( _tablelist )	Create subsources for specific tables upstream. Requires fully-qualified table names (<schema>.<table>).
RETAIN HISTORY FOR _retentionperiod	*Private preview. This option has known performance or stability issues and is under active development.* Duration for which Materialize retains historical data, which is useful to implement durable subscriptions. Accepts positive interval values (e.g. '1hr'). Default: 1s.

Creating a source

Materialize ingests the CDC stream for all (or a specific set of) tables in your upstream SQL Server database that have Change Data Capture enabled.

CREATE SOURCE mz_source
  FROM SQL SERVER CONNECTION sql_server_connection
  FOR ALL TABLES;

When you define a source, Materialize will automatically:

1. Create a subsource for each capture instance upstream, and perform an initial, snapshot-based sync of the associated tables before it starts ingesting change events.

   SHOW SOURCES;
   

            name         |   type     |  cluster  |
   ----------------------+------------+------------
    mz_source            | sql-server |
    mz_source_progress   | progress   |
    table_1              | subsource  |
    table_2              | subsource  |
   

2. Incrementally update any materialized or indexed views that depend on the source as change events stream in, as a result of INSERT, UPDATE and DELETE operations in the upstream SQL Server database.

It's important to note that the schema metadata is captured when the source is initially created, and is validated against the upstream schema upon restart. If you create new tables upstream after creating a SQL Server source and want to replicate them to Materialize, the source must be dropped and recreated.

SQL Server schemas

CREATE SOURCE will attempt to create each upstream table in the same schema as the source. This may lead to naming collisions if, for example, you are replicating schema1.table_1 and schema2.table_1. Use the FOR TABLES clause to provide aliases for each upstream table, in such cases, or to specify an alternative destination schema in Materialize.

CREATE SOURCE mz_source
  FROM SQL SERVER CONNECTION sql_server_connection
  FOR TABLES (schema1.table_1 AS s1_table_1, schema2.table_1 AS s2_table_1);

Monitoring source progress

[//]: # "TODO(morsapaes) Replace this section with guidance using the new progress metrics in mz_source_statistics + console monitoring, when available (also for PostgreSQL)."

By default, SQL Server sources expose progress metadata as a subsource that you can use to monitor source ingestion progress. The name of the progress subsource can be specified when creating a source using the EXPOSE PROGRESS AS clause; otherwise, it will be named <src_name>_progress.

The following metadata is available for each source as a progress subsource:

Field	Type	Details
lsn	bytea	The upper-bound Log Sequence Number replicated thus far into Materialize.

And can be queried using:

SELECT lsn
FROM <src_name>_progress;

The reported lsn should increase as Materialize consumes new CDC events from the upstream SQL Server database. For more details on monitoring source ingestion progress and debugging related issues, see Troubleshooting.

Known limitations

{{% include-md file="shared-content/sql-server-considerations.md" %}}

Examples

{{< important >}} Before creating a SQL Server source, you must enable Change Data Capture and SNAPSHOT transaction isolation in the upstream database. {{</ important >}}

Creating a connection

A connection describes how to connect and authenticate to an external system you want Materialize to read data from.

Once created, a connection is reusable across multiple CREATE SOURCE statements. For more details on creating connections, check the CREATE CONNECTION documentation page.

CREATE SECRET sqlserver_pass AS '<SQL_SERVER_PASSWORD>';

CREATE CONNECTION sqlserver_connection TO SQL SERVER (
    HOST 'instance.foo000.us-west-1.rds.amazonaws.com',
    PORT 1433,
    USER 'materialize',
    PASSWORD SECRET sqlserver_pass,
    DATABASE '<DATABASE_NAME>'
);

If your SQL Server instance is not exposed to the public internet, you can tunnel the connection through and SSH bastion host.

{{< tabs tabID="1" >}} {{< tab "SSH tunnel">}}

CREATE CONNECTION ssh_connection TO SSH TUNNEL (
    HOST 'bastion-host',
    PORT 22,
    USER 'materialize',
    DATABASE '<DATABASE_NAME>'
);

CREATE CONNECTION sqlserver_connection TO SQL SERVER (
    HOST 'instance.foo000.us-west-1.rds.amazonaws.com',
    SSH TUNNEL ssh_connection,
    DATABASE '<DATABASE_NAME>'
);

For step-by-step instructions on creating SSH tunnel connections and configuring an SSH bastion server to accept connections from Materialize, check this guide.

{{< /tab >}} {{< /tabs >}}

Creating a source {#create-source-example}

You must enable Change Data Capture, see Enable Change Data Capture SQL Server Instructions.

Once CDC is enabled for all of the relevant tables, you can create a SOURCE in Materialize to begin replicating data!

Create subsources for all tables in SQL Server

CREATE SOURCE mz_source
    FROM SQL SERVER CONNECTION sqlserver_connection
    FOR ALL TABLES;

Create subsources for specific tables in SQL Server

CREATE SOURCE mz_source
  FROM SQL SERVER CONNECTION sqlserver_connection
  FOR TABLES (mydb.table_1, mydb.table_2 AS alias_table_2);

Handling unsupported types

If you're replicating tables that use data types unsupported by SQL Server's CDC feature, use the EXCLUDE COLUMNS option to exclude them from replication. This option expects the upstream fully-qualified names of the replicated table and column (i.e. as defined in your SQL Server database).

CREATE SOURCE mz_source
  FROM SQL SERVER CONNECTION sqlserver_connection (
    EXCLUDE COLUMNS (mydb.table_1.column_of_unsupported_type)
  )
  FOR ALL TABLES;

Handling errors and schema changes

{{< include-md file="shared-content/schema-changes-in-progress.md" >}}

To handle upstream schema changes or errored subsources, use the DROP SOURCE syntax to drop the affected subsource, and then ALTER SOURCE...ADD SUBSOURCE to add the subsource back to the source.

-- List all subsources in mz_source
SHOW SUBSOURCES ON mz_source;

-- Get rid of an outdated or errored subsource
DROP SOURCE table_1;

-- Start ingesting the table with the updated schema or fix
ALTER SOURCE mz_source ADD SUBSOURCE table_1;

Related pages

• CREATE SECRET
• CREATE CONNECTION
• CREATE SOURCE