dbt - Advanced Patterns
Why does dbt snapshot use a unique_key instead of a primary key constraint to track records?
Why does dbt snapshot use a unique_key instead of a primary key constraint to track records?
hard🧠 Conceptual Q10 of 15
Step-by-Step Solution
Solution:
Step 1: Understand unique_key role in snapshots
Unique_key identifies records logically for tracking changes but does not enforce database constraints.Step 2: Clarify difference from primary keys
Primary keys are database constraints; snapshots do not require or enforce these constraints.Step 3: Evaluate other options
Primary keys are supported but not required. Unique_key does not create indexes automatically. Primary keys do not cause failures inherently.Final Answer:
Because unique_key identifies records logically without enforcing database constraints -> Option BQuick Check:
Unique_key = logical record ID, not DB constraint [OK]
Quick Trick: Unique_key tracks records logically, not as DB constraint [OK]
Common Mistakes:
MISTAKES- Confusing unique_key with primary key constraint
- Assuming unique_key creates indexes
- Believing primary keys cause snapshot errors
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