In a previous post , I explored Codd's connection trap in PostgreSQL and MongoDB — the classic pitfall where joining two independent many-to-many relationships through a shared attribute produces spurious combinations that look like facts but aren't. The example followed Codd's 1970 suppliers–parts–projects model: we know which suppliers supply which parts, and which projects use which parts, but joining through parts to derive supplier–project relationships is a relational composition — it tells us what could be true, not what is true. Oracle Database 26ai introduces JOIN TO ONE , a SQL extension that structurally prevents this class of errors. In this post, I'll reproduce Codd's connection trap in Oracle, show how JOIN TO ONE catches it, and demonstrate the correct solutions.…