Schema.rb understanding in Ruby on Rails - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a new table in schema.rb.

Ruby on Rails

create_table :users do |[1]|
  t.string :name
end

Drag options to blanks, or click blank then click option'

At

Buser

Ccolumn

Dtable

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'table' or 'user' instead of the block variable 't'.

Using 'column' which is not the block variable.

The block variable is usually t to define columns inside create_table.

2fill in blank

medium

Complete the code to add a datetime column for tracking record creation.

Ruby on Rails

t.[1] :created_at

Drag options to blanks, or click blank then click option'

Adate

Bdatetime

Ctimestamp

Dtime

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'timestamp' which is not the Rails schema.rb type.

Using 'date' or 'time' which store only part of the information.

In Rails schema.rb, datetime is used for date and time columns like created_at.

3fill in blank

hard

Fix the error in the schema.rb code to add a string column with a limit of 50 characters.

Ruby on Rails

t.string :username, [1]: 50

Drag options to blanks, or click blank then click option'

Alength

Bmax

Climit

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'length' or 'size' which are not valid options here.

Using 'max' which is not recognized.

The correct option to limit string length in schema.rb is limit.

4fill in blank

hard

Fill both blanks to add an index on the email column and make it unique.

Ruby on Rails

add_index :users, :email, [1]: true, [2]: 'index_users_on_email'

Drag options to blanks, or click blank then click option'

Aunique

Bname

Cindex_name

Dprimary

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'primary' instead of 'unique' for uniqueness.

Using 'index_name' which is not a valid option.

To add a unique index, use unique: true. The index name is set with name:.

5fill in blank

hard

Fill all three blanks to create a table without the default id column, with a text column, and timestamps.

Ruby on Rails

create_table :posts, id: [1] do |[2]|
  [2].text :content
  [2].timestamps
end

Drag options to blanks, or click blank then click option'

Afalse

Btrue

Ct

Dp

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'true' for id which includes the default id column.

Using 'p' as block variable which is uncommon.

Setting id: false disables default id. The block variable is t used to define columns and timestamps.

Practice

1. What is the main purpose of the schema.rb file in a Rails project?

easy

A. To show the current database tables and columns in Ruby code

B. To store user data permanently

C. To write application business logic

D. To manage user sessions

Solution

1. Step 1: Understand the role of schema.rb

   The schema.rb file represents the database structure in Ruby code format.

2. Step 2: Differentiate from other files

   It does not store data or application logic but shows tables and columns for easy sharing and recreation.

3. Final Answer:

   To show the current database tables and columns in Ruby code -> Option A

4. Quick Check:

   schema.rb = database structure [OK]

Hint: Remember: schema.rb maps database structure only [OK]

Common Mistakes:

• Thinking schema.rb stores actual data
• Confusing it with migration files
• Assuming it contains app logic

2. Which of the following is the correct syntax to define a string column named title in schema.rb?

easy

A. t.string :title

B. t.column :title, :integer

C. t.text 'title'

D. t.integer :title

Solution

1. Step 1: Identify correct column type syntax

   In schema.rb, string columns use t.string :column_name syntax.

2. Step 2: Check options

   t.string :title uses t.string :title, which is correct for a string column named title.

3. Final Answer:

   t.string :title -> Option A

4. Quick Check:

   String column syntax = t.string :title [OK]

Hint: Use t.string :name for string columns [OK]

Common Mistakes:

• Using t.integer for string columns
• Using quotes instead of symbols
• Confusing t.text with t.string

3. Given this snippet from schema.rb:

create_table "books", force: :cascade do |t|
  t.string "name"
  t.integer "pages"
  t.timestamps
end

What columns will the books table have?

medium

A. name (string), pages (string), timestamps (string)

B. name (string), pages (integer) only

C. name (string), pages (integer), created_at (datetime), updated_at (datetime)

D. name (text), pages (integer), timestamps (boolean)

Solution

1. Step 1: Read column definitions

   The table has name as string, pages as integer, and t.timestamps adds created_at and updated_at datetime columns.

2. Step 2: Confirm column types

   So columns are: name (string), pages (integer), created_at (datetime), updated_at (datetime).

3. Final Answer:

   name (string), pages (integer), created_at (datetime), updated_at (datetime) -> Option C

4. Quick Check:

   t.timestamps adds created_at and updated_at [OK]

Hint: Remember t.timestamps adds two datetime columns [OK]

Common Mistakes:

• Ignoring t.timestamps columns
• Assuming pages is string
• Confusing column types

4. You see this line in schema.rb but your migration added a price column as decimal:

t.integer :price

What is the likely problem?

medium

A. The price column is missing from the database

B. The migration syntax is wrong and created an integer column

C. Rails does not support decimal columns

D. The migration used decimal but schema.rb shows integer, so schema.rb is outdated

Solution

1. Step 1: Compare migration and schema types

   The migration added price as decimal, but schema.rb shows integer, indicating it was not updated.

2. Step 2: Understand schema.rb update process

   schema.rb updates only after running migrations successfully; if not updated, it shows old info.

3. Final Answer:

   schema.rb is outdated and shows integer instead of decimal -> Option D

4. Quick Check:

   Run migrations to update schema.rb [OK]

Hint: If types differ, check if migrations were run properly [OK]

Common Mistakes:

• Assuming Rails lacks decimal support
• Thinking migration syntax is always wrong
• Ignoring need to run migrations

5. You want to add a new published boolean column with default false to your articles table. After creating and running the migration, what will schema.rb show for this column?

hard

A. t.boolean :published

B. t.boolean :published, default: false

C. t.integer :published, default: 0

D. t.string :published, default: 'false'

Solution

1. Step 1: Understand migration effect on schema.rb

   Adding a boolean with default false will be reflected as t.boolean :published, default: false in schema.rb.

2. Step 2: Eliminate incorrect options

   t.boolean :published misses default, C uses wrong type integer, D uses string type incorrectly.

3. Final Answer:

   t.boolean :published, default: false -> Option B

4. Quick Check:

   Boolean with default shows type and default in schema.rb [OK]

Hint: Boolean defaults appear explicitly in schema.rb [OK]

Common Mistakes:

• Omitting default value in schema.rb
• Using wrong data type for boolean
• Confusing string and boolean types