Abstract. Database design aims to find a database schema that permits the efficient processing of common types of queries and updates on future database instances. Full first-order decompositions constitute a large class of database constraints that can provide assistance to the database designer in identifying a suitable database schema. We establish a finite axiomatisation of full first-order decompositions that reflects best database design practice: an inference engine derives all potential candidates of a database schema, but the final choice remains with the database designer. Key words: Database Decomposition, Database Constraint, Axiomatisation, Propositional Logic