unique_key

snapshots/<filename>.yml

snapshots:
  - name: orders_snapshot
    relation: source('my_source', 'my_table')
    config:
      unique_key: order_id

dbt_project.yml

snapshots:
  <resource-path>:
    +unique_key: column_name_or_expression

Description

A column name or expression that is unique for the inputs of a snapshot. dbt uses this to match records between a result set and an existing snapshot, so that changes can be captured correctly.

In Versionless and dbt v1.9 and later, snapshots are defined and configured in YAML files within your snapshots/ directory. You can specify one or multiple unique_key values within your snapshot YAML file's config key.

caution

Providing a non-unique key will result in unexpected snapshot results. dbt will not test the uniqueness of this key, consider testing the source data to ensure that this key is indeed unique.

Default

This is a required parameter. No default is provided.

Examples

Use an id column as a unique key

snapshots/orders_snapshot.yml

snapshots:
  - name: orders_snapshot
    relation: source('jaffle_shop', 'orders')
    config:
      schema: snapshots
      unique_key: id
      strategy: timestamp
      updated_at: updated_at

You can also specify configurations in your dbt_project.yml file if multiple snapshots share the same unique_key:

dbt_project.yml

snapshots:
  <resource-path>:
    +unique_key: id

Use multiple unique keys

You can configure snapshots to use multiple unique keys for primary_key columns.

snapshots/transaction_items_snapshot.yml

snapshots:
  - name: orders_snapshot
    relation: source('jaffle_shop', 'orders')
    config:
      schema: snapshots
      unique_key: 
        - order_id
        - product_id
      strategy: timestamp
      updated_at: updated_at