Consider a database schema with three relations:

Books$($bid:integer, bname:string, author:string, pubyear:integer, pubcompany:string$)$

Students$($sid:integer, sname:string, age:real, state:string$)$

Reads$($sid:integer,bid:integer,year:integer$)$

Primary keys are underlined in each relation. A book is uniquely identified by bid. A book has an id $($bid$),$ a name $($bname$),$ one author $($attribute author$),$ a publication year $($pubyear$),$ and a publishing company $($pubcompany$).$ A student is uniquely identified by sid. A student has an id $($sid$),$ a name $($attr$.$ sname$),$ age $($attr$.$ age$)$ and a state $($attr$.$ state$).$ If a student reads a book, a record will be present in the Reads relation, with that sid and bid and the year the book was read.