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One order can belong to three categories at once and my fact table keeps tripling the total.
What you'll have at the end
A bridge table between orders and categories, with one query that sums to the real total
You need
A fact table already loaded with real orders and their revenue, plus a tagging system that lets one order's product carry more than one category at once, where a category-level revenue report is coming out too high.
Not covered
A bridge table that also has to track when a tag relationship was true, which needs its own effective-dated setup underneath it.
Leans on
Design your first star schema
Start there if the many-to-many is really just several products on one order; splitting the grain can be the simpler fix than a bridge table.
Fix a warehouse total that's doubled
Go there instead when a total in production is already wrong and you're hunting for the cause, rather than designing a new bridge table from scratch.
Checked 25 Aug 2026
Part of the Data Warehousing cookbook