orders— one row per order, withcustomer_idandcreated_atreturns— one row per return, withcustomer_idandcreated_atcustomers— one row per customerdates— a date spine
orders and returns join to customers and dates, but they don’t
join to each other:
orders_count, total_revenue, returns_count,
and total_refunds grouped by customer and month. But joining orders and
returns directly would produce a cross product — every order matched with
every return for that customer and date — inflating all counts and sums.
How multi-fact views solve this
In a regular view, there is a single root cube — the first cube listed in the view’scubes array. All joins flow from this root, and
Cube uses it as the base table in the generated SQL.
Multi-fact views work differently. When a view includes measures from
multiple fact tables, Cube selects the root dynamically at query time
based on which measures are requested. Each fact table gets its own
aggregating subquery, and the results are joined on the shared dimensions.
No fanout, no manual workarounds.
How to model it
1. Define the cubes
Each fact table becomes a cube with explicit joins to the shared dimension tables:orders and returns declare direct joins to
customers and dates. This tells Cube that these dimension tables are shared
between the two facts.
2. Create a view
The view brings both fact tables and the shared dimension tables together. Dimension tables are included at root-level join paths (not nested under a specific fact), which makes their dimensions common to both facts. Useprefix to disambiguate identically named members across fact cubes:
orders_count, orders_total_amount, returns_count, and
returns_total_refund grouped by name, city, and date, Cube detects
the two separate fact roots and automatically executes a multi-fact query.
What Cube does under the hood
Cube executes the query in three stages:1. Separate aggregating subqueries
Each fact table gets its own independent subquery that joins only the tables it needs, applies relevant filters, and aggregates by the common dimensions:- Subquery 1 (orders): joins
orders→customersandorders→dates, computesCOUNT(*)andSUM(amount), grouped byname,city,date - Subquery 2 (returns): joins
returns→customersandreturns→dates, computesCOUNT(*)andSUM(refund_amount), grouped byname,city,date
2. Join on common dimensions
The subquery results are joined withFULL JOIN on all common dimension
columns (name, city, date). This preserves rows that exist in only one
fact table — a customer who placed orders but never returned anything still
appears in the results.
3. Final result
The combined result shows measures from each fact table side by side:| name | city | date | orders_count | orders_total_amount | returns_count | returns_total_refund |
|---|---|---|---|---|---|---|
| Alice | New York | 2025-01-15 | 2 | 200.00 | 0 | NULL |
| Alice | New York | 2025-02-10 | 2 | 225.00 | 1 | 100.00 |
| Bob | Seattle | 2025-01-20 | 3 | 550.00 | 2 | 130.00 |
| Charlie | New York | 2025-02-05 | 0 | NULL | 2 | 100.00 |
| Diana | Boston | 2025-03-01 | 1 | 400.00 | 0 | NULL |
NULL values for the missing fact table.
Common patterns
Time as the shared dimension
The most common multi-fact pattern uses time as the shared dimension. For example, you might havepage_views, signups, and purchases that all
have timestamps but no direct relationship. By joining each to a shared
dates cube, you can analyze conversion funnels — page views vs. signups
vs. purchases by day — without any row multiplication.
More than two fact tables
Multi-fact queries are not limited to two fact tables. If a view includes three or more facts, each gets its own aggregating subquery, and all results are joined on the common dimensions.Facts that don’t share all dimensions
Every root fact table must be joinable to the same set of common dimension tables. If a fact table doesn’t naturally have a foreign key for one of the common dimensions, you can create a synthetic join:NULL AS customer_id makes the join syntactically valid. Refund rows
won’t match a specific customer, but the subquery can still participate in
the multi-fact join on the full set of common dimensions.
Filters and segments
Common dimension filters (likecity = 'New York' or date > '2025-01-01')
are applied to every subquery, ensuring consistent filtering across all facts.
Fact-specific filters (like orders.status = 'completed') are applied only
to that fact’s subquery. Other fact subqueries remain unaffected.
Measure filters (like orders_count > 1) are applied as HAVING
conditions after the subqueries are joined.
Segments that belong to a specific fact table are applied only
to that fact’s subquery.
Join path requirements
- Each fact cube must declare direct joins to all shared dimension tables
- Dimension tables should be included in the view at root-level join paths,
not nested under a specific fact (e.g.,
customers, notorders.customers) - Use
prefixon fact cubes to disambiguate identically named members