SQL Server Batch Query Connector

This connector captures data from SQL Server databases into Flow collections by periodically executing queries and translating the results into JSON documents.

When to use this connector

We recommend using our SQL Server CDC Connector instead when possible. CDC provides lower latency data capture, delete and update events, and typically has a smaller impact on the source database.

However, the batch connector is the right choice when:

• Your SQL Server instance doesn't support CDC (e.g., some managed services)
• You need to capture from database views
• You want to execute ad-hoc or custom queries

Supported versions and platforms

This connector works with all supported versions of SQL Server on major cloud platforms (including Amazon RDS, Azure SQL Database, and other managed services), as well as self-hosted instances.

Configuration Tip

To capture data from databases hosted on your internal network, you may need to use SSH tunneling. If you have a private deployment, you can also use private cloud networking features to reach your database.

Prerequisites

You'll need:

• A SQL Server database with a user that has SELECT permission on the tables you want to capture
• Network access to the database (direct or via SSH tunnel)

Setup

Creating a capture user

We recommend creating a dedicated user for Flow captures:

CREATE LOGIN flow_capture WITH PASSWORD = 'secret';
CREATE USER flow_capture FOR LOGIN flow_capture;

Grant read permissions on the tables you want to capture:

-- Grant SELECT on a specific schema
GRANT SELECT ON SCHEMA::dbo TO flow_capture;

-- Or grant SELECT on all schemas
GRANT SELECT ON DATABASE::my_database TO flow_capture;

Replace dbo or my_database with the name of your schema or database, or grant permissions on multiple schemas as needed.

Usage

Query behaviors

The connector executes queries periodically to capture data. It defaults to a built-in query template which supports three patterns of use:

• Full-refresh (no cursor): The entire table/view is re-read on each poll.
• Cursor-incremental: Captures rows where the cursor has advanced since we last polled, according to WHERE cursor > $lastValue ORDER BY cursor.
• Custom query: Override the built-in template to execute arbitrary SQL. This may be useful for filtering, aggregations, or subsets of your data.

Common cursor choices:

• Update timestamps: Best when available, as they capture both new rows and updates
• Creation timestamps: Work for append-only tables but won't detect updates
• Auto-incrementing IDs: Work for append-only tables but won't detect updates

When no cursor is configured, the entire table or view is re-read on each poll.

Data Volume Consideration

Full-refresh bindings re-capture all data on each poll, which can generate significant data volumes. A few megabytes polled every hour adds up to gigabytes per day. Use cursors or longer polling intervals to manage data volume when capturing views or tables without suitable cursors.

Polling schedule

The connector executes queries on a configurable schedule, which may be set at the capture level and/or overridden on a per-binding basis. When unset, the schedule defaults to polling every 24 hours.

Polling intervals are written as strings in one of two formats:

• Interval format: 5m (5 minutes), 1h (1 hour), 24h (24 hours), etc
• Time-of-day format: daily at 12:34Z (daily at 12:34 UTC)
  • Time-of-day polling schedules must specify the time in UTC with the 'Z' suffix. Other timezones or offsets are not currently supported.

Time zone handling

SQL Server DATETIME, DATETIME2, and SMALLDATETIME columns don't include time zone information. The connector converts these to RFC3339 timestamps by interpreting them in the time zone configured in /advanced/timezone (defaults to UTC).

The DATETIMEOFFSET type includes time zone information and is preserved as-is.

Collection keys

Discovered tables with primary keys will use them as their collection keys. Tables without a primary key use /_meta/row_id as the collection key.

When a full-refresh binding outputs to a collection keyed by /_meta/row_id, the connector can infer deletions: if a refresh yields fewer rows than the previous poll, deletion documents are emitted for the missing row IDs.

Configuration

Configure this connector in the Flow web app or using YAML config files with flowctl CLI. See connectors to learn more about using connectors.

Endpoint Properties

Property	Title	Description	Type	Required/Default
/address	Server Address	The host or host:port at which the database can be reached.	string	Required
/user	User	The database user to authenticate as.	string	Required, "flow_capture"
/password	Password	Password for the specified database user.	string	Required
/database	Database	Logical database name to capture from.	string	Required
/advanced	Advanced Options	Options for advanced users. You should not typically need to modify these.	object
/advanced/poll	Default Polling Schedule	When and how often to execute fetch queries. Accepts a Go duration string like '5m' or '6h' for frequency-based polling, or a string like 'daily at 12:34Z' to poll at a specific time (specified in UTC) every day.	string	"24h"
/advanced/discover_views	Discover Views	When set, views will be automatically discovered as resources. If unset, only tables will be discovered.	boolean	false
/advanced/discover_schemas	Discovery Schema Selection	If this is specified, only tables in the selected schema(s) will be automatically discovered. Omit all entries to discover tables from all schemas.	array	[]
/advanced/timezone	Time Zone	The IANA timezone name in which datetime columns will be converted to RFC3339 timestamps. Defaults to UTC if left blank.	string	"UTC"
/advanced/source_tag	Source Tag	When set, the capture will add this value as the property 'tag' in the source metadata of each document.	string
/networkTunnel	Network Tunnel	Connect to your system through an SSH server that acts as a bastion host for your network.	object

Binding Properties

Property	Title	Description	Type	Required/Default
/name	Resource Name	The unique name of this resource.	string	Required
/schema	Schema Name	The name of the schema in which the captured table lives. Must be set unless using a custom template.	string
/table	Table Name	The name of the table to be captured. Must be set unless using a custom template.	string
/cursor	Cursor Columns	The names of columns which should be persisted between query executions as a cursor.	array	[] (full-refresh)
/poll	Polling Schedule	When and how often to execute the fetch query (overrides the connector default setting). Accepts a Go duration string like '5m' or '6h' for frequency-based polling, or a string like 'daily at 12:34Z' to poll at a specific time (specified in UTC) every day.	string
/template	Query Template Override	Optionally overrides the query template which will be rendered and then executed.	string

Type mapping

SQL Server types are mapped to JSON types as follows:

SQL Server Type	JSON Type	Notes
BIT	boolean
TINYINT, SMALLINT, INT, BIGINT	integer
FLOAT, REAL	number
NUMERIC, DECIMAL, MONEY, SMALLMONEY	string	Formatted as number string with format number to preserve precision
CHAR, VARCHAR, TEXT, NCHAR, NVARCHAR, NTEXT, XML	string
BINARY, VARBINARY, IMAGE	string	Bytes encoded as base64 string
DATE	string	Format: date
TIME	string	Format: time
DATETIME, DATETIME2, SMALLDATETIME	string	Format: date-time (RFC3339), interpreted in configured timezone
DATETIMEOFFSET	string	Format: date-time (RFC3339), timezone preserved
UNIQUEIDENTIFIER	string	Format: uuid

Query templates

Query templates use Go's template syntax to generate SQL queries. The connector uses a default template which implements appropriate behavior for full-refresh and cursor-incremental bindings, but you can override this for custom behavior.

Overriding the query template is best left to power-users or done at the direction of Estuary support. Consult the connector source for the current text of the default template.