Relation Schema and Instance A1,A2,...,An are attributes R=(A,A2,...,A is a relation schema Example: instructor =(ID,name,dept name,salary) A relation instance r defined over schema R is denoted by r(R) The current values a relation are specified by a table An element t of relation ris called a tuple and is represented by a row in a table Database System Concepts-7th Edition 2.4 @Silberschatz,Korth and SudarshanDatabase System Concepts - 7 2.4 ©Silberschatz, Korth and Sudarshan th Edition Relation Schema and Instance ▪ A1 , A2 , …, An are attributes ▪ R = (A1 , A2 , …, An ) is a relation schema Example: instructor = (ID, name, dept_name, salary) ▪ A relation instance r defined over schema R is denoted by r (R). ▪ The current values a relation are specified by a table ▪ An element t of relation r is called a tuple and is represented by a row in a table