DatabaseQuery Optimization, Data Modeling
KW-0001Fanout Join
Problem
Meaning
joining tables in a way that multiplies rows (usually in one-to-many relationships), causing incorrect aggregations like inflated sums or counts
Example
“Joining orders with order_items and then summing order total results in duplicated totals per item”
Reference
Common in reporting queries; must aggregate before join or use subqueries. Often discussed as “this join is causing duplication”
Related
join explosionaggregation errorone-to-many joingrouping