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Databases and Model Classes

Explore software engineering aspects like requirements, testing, and more with a focus on databases and model classes. Learn about DBMS, SQL, relational models, CRUD mapping, and data manipulation using examples and resources. Discover how Rails leverages DBMS and ORM for efficient data handling.

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Databases and Model Classes

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  1. http://flic.kr/p/ar4nLn Databases and Model Classes

  2. 4 SWEBOK KAs covered so far Today’s topics • Software Requirements • Software Design • Software Construction • Software Testing • Software Maintenance • Software Configuration Management • Software Engineering Management • Software Engineering Process • Software Engineering Models and Methods • Software Quality • Software Engineering Professional Practice • Software Engineering Economics • Computing Foundations • Mathematical Foundations • Engineering Foundations

  3. Database (DB): Organized collection of data Database Management System (DBMS): Controls the creation, maintenance, and use of a DB http://flic.kr/p/ar4nLn

  4. RecallRails MVC Rails uses a DBMS!

  5. Why use a DBMS? • Data independence: Applications need not be concerned with how data is stored or accessed • Provides a lot of functionality that would be silly to implement yourself: • Sharing (network) • Customizable security • Integrity

  6. Two key aspects of a DBMS • Database model: How DB is structured and used • Examples: Relational, Object-Oriented, Hierarchical • Query language: Types of questions you can ask • Examples: SQL, XQuery Relational + SQL is most common and use by Rails

  7. Relational Model Concepts http://en.wikipedia.org/wiki/File:Relational_model_concepts.png

  8. Example Tables Authors AuthorISBN Publishers Titles

  9. Primary versus Foreign Keys • Primary key: Uniquely identifies each record in table • Foreign key: Field in table A such that the field is a primary key in one other table B Authors AuthorISBN

  10. Example Foreign Keys Authors AuthorISBN Publishers Titles

  11. CRUD-to-SQL Mapping For complete documentation, see: http://dev.mysql.com/doc/refman/5.5/en/sql-syntax-data-manipulation.html

  12. Example SELECT Queries • SELECT * FROM Authors • SELECT AuthorID, LastName FROM Authors • SELECT * FROM Authors WHERE YearBorn > 1910 • SELECT * FROM Authors WHERE LastName LIKE ‘r%’ • SELECT * FROM Authors WHERE LastName LIKE ‘_e%’ • SELECT * FROM Authors WHERE LastName REGEXP ‘[a-r]*’ • SELECT * FROM Authors WHERE LastName REGEXP ‘[a-r]*’ORDER BY LastName ASC For complete documentation, seehttp://dev.mysql.com/doc/refman/5.5/en/select.html http://dev.mysql.com/doc/refman/5.5/en/pattern-matching.html

  13. Use JOIN to merge data from multiple tables • SELECTFirstName, LastName, ISBNFROM Authors INNER JOIN AuthorISBN ON Authors.AuthorID = AuthorISBN.AuthorIDORDER BY LastName, FirstName • SELECT Titles.Title, Authors.LastName, Publishers.PublisherNameFROM (Publishers INNER JOIN Titles ON Publishers.PublisherID = Titles.PublisherID)INNER JOIN (Authors INNER JOIN AuthorISBN ON Authors.AuthorID = AuthorISBN.AuthorID)ON Titles.ISBN = AuthorISBN.ISBN For complete documentation, seehttp://dev.mysql.com/doc/refman/5.5/en/join.html

  14. RecallRails MVC You writeOO Ruby But DB knows relational/SQL How to reconcile these diffs?

  15. Class with no associations ???

  16. Class with no associations

  17. One-to-many association ???

  18. One-to-many association

  19. Many-to-many association ???

  20. Many-to-many association

  21. Generalization ???

  22. Generalization

  23. Ruby provides anObject-Relational Mapping (ORM)systemLet’s see how it works…Go to: http://web.stanford.edu/~ouster/cgi-bin/cs142-fall10/lecture.php?topic=activeRecord

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