The interface
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AddBook(Book):boolean
UpdateBook(Book):boolean
DeleteBook(String id):boolean
GetBook(int id):Book


AddEmployee(Employee):boolean
UpdateEmployee(Employee):boolean
DeleteEmployee(int id):boolean
GetEmployee(int id):Employee

borrowBook(int bookId, int empId, Date borrowedDate):boolean
returnBook(BorrowingRecord br):boolean
getLastBorrowingRecord(int book_id):BorrowingRecord

Table structure
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book(id, name, author, description)
employee(id, name)
borrowings(book_id, emp_id, borrowed_date, returned_date)