We proposed an approach to local lossless join preservation, in contrast to the global lossless join preservation of relational database schema. The database designer, using the so-called form types, creates relational database views. These form types contain all information, necessary to design the set of database constraints. We identify criteria to be satisfied if a subschema with lossless join should be designed. It was also shown that for each form type used in the process of designing the database schema subschema, satisfying the lossless join condition, can be generated.