Database and Active Record

6th lecture, May 20, 2019

Projects in Information Technology II

Martin J. Dürst


© 2019 Martin J. Dürst 青山学院大学



Today's Schedule


Last Lecture's Exercises

Always start ERB templates with <!DOCTYPE,
not with <%... Ruby code


Course Overview



title authors isbn price ...
Agile Web Development Sam, Dave, David 978-1-68050-171-1 $46.00 ...
Programming Ruby Dave with Chad and Andy 978-1-93778-549-9 $50.00 ...
Learning Rails 5 Mark, Barnabas, Eric 978-1-491-92619-2 $44.00 ...
... ... ... ... ...


Database Engines


Object-Relational Mapper/Mapping (ORM)


How to Use Active Record (Indepedently)

(this week, we are using Active Record independently of Rails)


What Active Record Does

Active Record does the following automatically:


Configuration or Convention


Convention over Configuration


How to Create a New Database Entry

(examples for table books)


How to Retrieve Entries from the Database


Access to Objects


Column Statistics


Database used for Exercises


Exercise 6a: Calculate Wrestler Statistics


Exercise 6b: Web Page with Wrestler Table


Exercise 6c: Advanced Exercise (発展問題):