What will happen if you run this dbt model with is_incremental() logic and the target table is empty?

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dbt - Incremental Models

What will happen if you run this dbt model with is_incremental() logic and the target table is empty?

{% if is_incremental() %}
  SELECT * FROM source_table WHERE id > (SELECT MAX(id) FROM {{ this }})
{% else %}
  SELECT * FROM source_table
{% endif %}

AAll rows from source_table will be inserted

BNo rows will be inserted because MAX(id) returns NULL

COnly rows with id greater than NULL will be inserted

DThe model will fail with a syntax error

Step-by-Step Solution

Solution:

Step 1: Understand MAX(id) on empty table
MAX(id) returns NULL if the target table is empty.
Step 2: Evaluate the WHERE clause with NULL
Comparing id > NULL yields false, so no rows match.
Final Answer:
No rows will be inserted because MAX(id) returns NULL -> Option B
Quick Check:
MAX on empty = NULL, comparison fails [OK]

Quick Trick: MAX on empty table returns NULL, blocking incremental inserts [OK]

Common Mistakes:

MISTAKES

Assuming NULL comparison returns true
Expecting all rows to insert on empty table
Thinking model will error out

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What will happen if you run this dbt model with is_incremental() logic and the target table is empty?

Step 1: Understand MAX(id) on empty table

Step 2: Evaluate the WHERE clause with NULL

Final Answer:

Quick Check:

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