employee department project dependent works for manages works on dependents of controls supervision bdate ssn name lname minit fname sex address salary birthdatenamesex relationship name numberlocation name number number of employees startdate hours 1 1 1 N supervisor supervisee M N 1 1 N N degree location
Mapping from ER-diagrams onto relational schemas 1.Create a relation for each strong entity type 2. Create a relation for each weak entity type 3. For each binary 1:1 relationship choose an entity and include the other’s PK in it as an FK 4. For each binary 1:n relationship, choose the n-side entity and include an FK with respect to the other entity. 5. For each binary M:N relationship, create a relation for the relationship 6. For each multi-valued attribute create a new relation 7. For each n-ary relationship, create a relation for the relationship
About participation constraints If a relationship is mandatory for an entity set, then if the entity set is on the “many” side of the relationship, then a specification is required to ensure a foreign key has a value, and that it cannot be null setting the ‘required’ property for the FK in MS Access, or NOT NULL constraint in the DDL. N A c d B x y 1
cd A xyc B The “required” property for attribute c is set “yes”.