DBT DBT Snapshots & Incremental Models 3

Question 1

What does the `invalidate_hard_deletes` config on a dbt snapshot do?

Accepted Answer

Sets dbt_valid_to on snapshot rows whose source rows have been deleted

Answer

When `invalidate_hard_deletes: true`, dbt closes out snapshot rows for source records that no longer exist by setting `dbt_valid_to` to the current timestamp.

Question 2

Which `incremental_strategy` inserts all new rows without checking for duplicates, suitable for append-only event streams?

Accepted Answer

append

Answer

The `append` strategy simply inserts new rows without any deduplication or updating, ideal for immutable event logs.

Question 3

What happens to an incremental model on its very first run when the target table does not yet exist?

Accepted Answer

It runs as a full table build, ignoring the is_incremental() filter

Answer

On the first run, `is_incremental()` returns false because the table doesn't exist, so dbt executes the full query and creates the table.

Question 4

In a dbt snapshot using the `check` strategy, what must you specify under `check_cols`?

Accepted Answer

The list of columns whose changes should be tracked

Answer

`check_cols` lists the specific columns dbt should hash and compare; if any of them change, a new snapshot row is created.

Question 5

Which column added by dbt snapshots holds a hash of all snapshot-tracked columns for change detection?

Accepted Answer

dbt_scd_id

Answer

`dbt_scd_id` is a hash-based unique identifier generated by dbt for each snapshot row, combining the unique key and `dbt_updated_at` to ensure row-level uniqueness.

DBT - Certified Data Build Tool Developer Practice Test

DBT - Certified Data Build Tool Developer Practice Test

DBT DBT Snapshots & Incremental Models 3