Question 1

Does this pairing support change data capture?

Accepted Answer

No, and it is the most important thing to know before relying on the copy. Syncing from Azure SQL uses a tracking column rather than a change feed: you nominate a monotonically increasing column such as an updated timestamp, the first run reads everything, and later runs read rows beyond the last recorded position. That works well for append heavy and steadily updated tables, but it is watermarking rather than a changelog.

Question 2

What happens to rows deleted in Azure SQL?

Accepted Answer

They stay in MotherDuck. Because the sync only sees rows whose tracking value has advanced, a deleted row simply stops appearing at the source and the copy keeps it indefinitely. A row edited without its tracking column advancing is missed for the same reason. If delete accuracy or edit completeness matters for your reporting, schedule a periodic full resync into MotherDuck to reconcile rather than assuming incremental keeps parity.

Question 3

Do incremental runs merge or append?

Accepted Answer

They merge when the table has a primary key. MotherDuck loads through Parquet staging, but that is transport only: rows land in a staging table and the destination is then reconciled with update and insert statements, so an updated row replaces its previous version rather than sitting alongside it. Without a primary key the load falls back to append, which is fine for event shaped data and misleading for anything mutable.

Question 4

Why replicate Azure SQL into MotherDuck?

Accepted Answer

Because analytical queries and application queries want different things from the same database. Reporting against Azure SQL competes with the workload serving your users, and joining application data to billing, CRM, and support systems is not something one database does well. Running ETL into MotherDuck moves that load onto an engine built for it, and gives analysts SQL over a copy they cannot disrupt production with.

Connect MotherDuck with Azure SQL

Connect MotherDuck and Azure SQL with Polytomic

Tracking column incremental

Deletes are not detected

Keyed merges into MotherDuck

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