Entity Sets An entity is an object that exists and is distinguishable from other objects Example:specific person,company,event,plant An entity set is a set of entities of the same type that share the same properties. Example:set of all persons,companies,trees,holidays An entity is represented by a set of attributes;i.e.,descriptive properties possessed by all members of an entity set. ·Example: instructor=(ID,name,salary) course=(course_id,title,credits) A subset of the attributes form a primary key of the entity set;i.e., uniquely identifying each member of the set. Database System Concepts-7th Edition 6.10 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 6.10 ©Silberschatz, Korth and Sudarshan th Edition Entity Sets ▪ An entity is an object that exists and is distinguishable from other objects. • Example: specific person, company, event, plant ▪ An entity set is a set of entities of the same type that share the same properties. • Example: set of all persons, companies, trees, holidays ▪ An entity is represented by a set of attributes; i.e., descriptive properties possessed by all members of an entity set. • Example: instructor = (ID, name, salary ) course= (course_id, title, credits) ▪ A subset of the attributes form a primary key of the entity set; i.e., uniquely identifying each member of the set