This document discusses the benefits of using an object-relational mapping (ORM) framework. It explains that ORMs allow developers to work with objects in code while the ORM handles the conversion between objects and relational data in the database. This avoids the need to write manual SQL queries and allows developers to focus on business logic rather than data access code. The document also provides examples of how ORMs can efficiently execute queries and fetch records from the database.

1. ORM

2. Why ORM?

3. Why ORM?
•

4. Why ORM?
•
• SQL

5. Why ORM?
•
• SQL

6. Why ORM?
•
• SQL
•

7. O - Object

8. O - Object
•

9. O - Object
•
• Admin inherits User ?

10. R - Relational

11. R - Relational
• CRUD

12. R - Relational
• CRUD
• 3NF

13. R - Relational
• CRUD
• 3NF
•

14. M - Mapping

15. M - Mapping
• O => R ?

16. M - Mapping
• O => R ?
• R => O ?

17. R=>O
•
•

18. ActiveRecord
•
•
•

19. • ORM =
•

21. •

22. •
•

23. •
•

24. •
•
•

25. N + 1 VS 1

26. N + 1 VS 1
• select * from blogs

27. N + 1 VS 1
• select * from blogs

28. N + 1 VS 1
• select * from blogs

29. N + 1 VS 1
• select * from blogs
• select id from blogs

30. N + 1 VS 1
• select * from blogs
• select id from blogs
• select * from blogs where id=X

31. • Objects
• Lists

33. • FetchById

34. • FetchById
•

35. • FetchById
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•

36. • FetchById
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•

37. • FetchById
•
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• FetchByIds

38. • select * from blogs where user_id = XXX
order by id desc
•

39. • where column1 = XXX
• and column2=YYY
• order by id desc
• count(*)

40. • Query q = Blogs.Query();
• q.AddWhere(“user_id”, XXX);
• q.OrderBy(“id”, “desc”);
• q.Start = 0;
• q.count = 10;
• q.ExecuteIds();

41. • Query q = Blogs.Query();
• ....
• q.CountIds();

43. •

44. •

45. •
•

46. •
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• Delete by old value

47. •
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• Delete by old value
• Add by new value

48. •
•
•

49. • SubSonic http://subsonicproject.com/
• Cache Money http://github.com/nkallen/
cache-money
• PEAA http://book.douban.com/subject/
1230559/