[Solved] You have three dbt source models: orders, refunds, and customers.... Which approach best applies the multi-source fan-in pattern? | dbt

dbt - Advanced Patterns

You have three dbt source models: orders, refunds, and customers. You want to build a fan-in model that reports total net sales per customer. Which approach best applies the multi-source fan-in pattern?

ACreate separate models for each source and union them without joins.

B

Join <code>orders</code> and <code>refunds</code> on <code>order_id</code>, aggregate net sales, then join with <code>customers</code> on <code>customer_id</code>.

CJoin <code>customers</code> directly with <code>orders</code> only, ignoring refunds.

DUse a CROSS JOIN between all three sources to combine all rows.

Step-by-Step Solution

Solution:

Step 1: Understand the goal
We want net sales per customer, which requires combining orders and refunds.
Step 2: Apply multi-source fan-in
First join orders and refunds on order_id to calculate net sales, then join with customers on customer_id to attribute sales.
Final Answer:
Join orders and refunds on order_id, aggregate net sales, then join with customers on customer_id. -> Option B
Quick Check:
Aggregate related sources before joining to customers [OK]

Quick Trick: Aggregate related sources before joining customers [OK]

Common Mistakes:

MISTAKES

Ignoring refunds when calculating net sales
Using CROSS JOIN causing data explosion
Unioning sources without joining on keys

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Which approach best applies the multi-source fan-in pattern?

Step 1: Understand the goal

Step 2: Apply multi-source fan-in

Final Answer:

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