A client with a three-level hierarchy — Top Group, Group, Client — where not all branches are complete. How I balanced a ragged hierarchy with self-parenting: whoever has no parent becomes their own parent.
A sales director asks how many customers were in the North region last June. The DWH can't answer because every update overwrites previous data. How I implemented an SCD Type 2 with surrogate keys and validity dates to give the business back its historical memory.
A fact table built on monthly invoice totals looked perfect. Then the business asked for product-level, line-level, customer-level detail. And the data warehouse went silent.