“Show me your flowcharts and conceal your tables, and I shall continue to be mystified. Show me your tables, and I won't usually need your flowcharts; they'll be obvious.”Frederick P. Brooks Jr. · The Mythical Man-Month · 1975 · The Mythical Man-Month (1975), cap. 9 — Ten Pounds in a Five-Pound Sack
A well-named, well-keyed table is the best documentation you will ever write.
Brooks said the tables explain the system; in a warehouse, the tables are the system. The first cause of failure is the missing model: sources copied side by side and called a "warehouse", with no facts and dimensions, no shared definition of "customer" or "revenue" — hence three reports with three figures. The second is the missing owner: datasets nobody answers for, without tests, where a column renamed at the source goes unnoticed for a month. The third is the missing user: a warehouse built "for when we will need it", instead of for a concrete decision on Monday morning. The rest is a checklist, briefly. Surrogate and natural keys confused, joins that multiply rows. Time zones and currencies mixed in the same column. Event time confused with load time. The NULL that disappears from aggregates and joins without notice. Unbounded queries in a system billed per read. Personal data on every row, with no vault and no deadline. Streaming where a daily load was enough. And missing documentation — although, as Brooks says, a well-named, well-keyed table is the best documentation you will ever write.
Why it matters No tool makes up for a missing model, an ownerless dataset or a warehouse without a user. All three show in the tables, if you look.