Ruby & Databases Recap Quiz for Week 2 [Solutions]

gistfile1.txt

## Week 3 Quiz


## 1) What does ORM stand for?


Object Relationship Mapper




## 2) What are the four functions of persistent storage? (hint: CRUD)





Create Read Update Delete







## 3) The result is 'princess bride' what was the query? You can use Ruby (ActiveRecord) or SQL

    class User < ActiveRecord::Base

    end

        ------------------------------------
        | Users Table                      |
        +----+---------+-------------------+
        | ID | Name    | Movie             |
        |----+---------+-------------------|
        | 1  | Richard | zoolander         |
        |----+---------+-------------------|
        | 2  | Ruby    | princess bride    |
        |----+---------+-------------------|
        | 3  | Chris   | sandlot           |
        +----+---------+-------------------+



SELECT movie FROM users WHERE name = 'Ruby';

or

User.where(:name => 'Ruby').first.name





## 4) What type of key does the ID column represent in the Users table above

  A) Foreign

  B) Primary

  C) Public

  D) Private


The answer is A) Primary



## 5) MIN is a database function, list one more

COUNT
MAX
AVG
and many more





## 6) In Rails we could build a blog. On each blog post we might want comments. We could say that a Post has_many :comments and that a Comment belongs to :post.

    class Post < ActiveRecord::Base
      has_many :comments
    end

    class Comment < ActiveRecord::Base
      belongs_to :post
    end

A post has properties :title, :author_name, and :body, a comment has properties :name & :body. Sketch out a posts table and a comments table including the primary and foreign keys. Use this data:


    1) "John" wrote a post titled "I love dogs" with the content "woof", "richard" commented "that was great", susan commented "cats are better"

    2) "Sara" wrote a post titled "cars are great" with the content " I think they are", "james" commented  "they are"


Sketch this out so it looks like the users table above

(formatted using http://www.sensefulsolutions.com/2010/10/format-text-as-table.html )

      Posts Table
      +----+----------------+-------------+-------------------+
      | ID |     title      | author_name |   body            |
      +----+----------------+-------------+-------------------+
      |  1 | I love dogs    | john        | woof              |
      |  2 | cars are great | sara        | I think they are  |
      +----+----------------+-------------+-------------------+

      Comments Table
      +----+---------+-----------------+---------+
      | ID |  name   |      body       | post_id |
      +----+---------+-----------------+---------+
      |  1 | richard | that was great  |       1 |
      |  2 | susan   | cats are better |       1 |
      |  3 | james   | they are        |       2 |
      +----+---------+-----------------+---------+























## 7) Using only Ruby (ActiveRecord) and using the data from the above example, how would we find all the posts that were written by "john".





Post.where(:author_name => 'john').first











## 8) What is the output of the following


    puts "hello".class


    # => String






    puts {:bird => 'tweet'}.class


    # => Hash





    class Adult
    end

    class Child < Adult
    end

    little_richie = Child.new

    puts little_richie.class


    # => Child




Hints:

select, where, count, from, *, =

I believe for question number 3 it should be in Ruby:
User.where(:name => 'Ruby').first.movie
or simplified:
User.where(name:'Ruby').movie

Agreed with MrBri.. "name" would just return "Ruby" again.

Number 4 should be changed to:

B) Primary

Ya, I agree with both the fixes described above.

Think the answer for #7 should be:

Post.where(:author_name => 'john')

— without the "first" since we're looking for all entries?