Django Features and Libraries | Week 4

Course Name: Django for Everybody

Sub-course: Django Features and Libraries

Course Link: Django for Everybody

Sub-course Link: Django Features and Libraries

These are Django Features and Libraries Week 4 Answers Coursera Quiz

One to Many

Q1. What is the primary value add of relational databases over flat files?

  • Ability to execute JavaScript in the file
  • Ability to quickly convert data to HTML
  • Ability to execute Python code within the file
  • Ability to scan large amounts of data quickly
  • Ability to store data in a format that can be sent across a network

Answer: Ability to scan large amounts of data quickly

Q2. Which of the following is NOT a good rule to follow when developing a database model?

  • Use integers as primary keys
  • Use a person’s email address as their primary key
  • Model each “object” in the application as one or more tables
  • Never repeat string data in more than one table in a data model

Answer: Use a person’s email address as their primary key

These are Django Features and Libraries Week 4 Answers Coursera Quiz

Q3. If our user interface (i.e., like iTunes) has repeated strings on one column of the UI, how should we model this properly in a database?

  • Put the string in the first row where it occurs and then NULL in all of the other rows
  • Put the string in the last row where it occurs and put the number of that row in the column of all of the rest of the rows where the string occurs
  • Make a table that maps the strings in the column to numbers and then use those numbers in the column
  • Put the string in the first row where it occurs and then put that row number in the column of all of the rest of the rows where the string occurs
  • Encode the entire row as JSON and store it in a TEXT column in the database
See also  Using JavaScript and JSON in Django | Week 4

Answer: Make a table that maps the strings in the column to numbers and then use those numbers in the column

Q4. Which of the following is the label we give a column that the “outside world” uses to look up a particular row?

  • Logical key
  • Local key
  • Primary key
  • Foreign key
  • Remote key

Answer: Logical key

These are Django Features and Libraries Week 4 Answers Coursera Quiz

Q5. What is the label we give to a column that is an integer and is used to point to a row in a different table?

  • Foreign key
  • Primary key
  • Logical key
  • Remote key
  • Local key

Answer: Foreign key

Q6. What is a simple rule that captures much of the concepts of “database normalization”?

  • Don’t use any non-standard SQL statements
  • Do not point to a primary key more than once
  • Every SELECT statement must use a JOIN clause
  • Don’t replicate string data in a column

Answer: Don’t replicate string data in a column

These are Django Features and Libraries Week 4 Answers Coursera Quiz

Q7. What is the SQL keyword that reconnects rows containing foreign keys with the corresponding data in the table that the foreign keys point to?

  • CONNECT
  • COUNT
  • APPEND
  • CONSTRAINT
  • JOIN

Answer: JOIN

These are Django Features and Libraries Week 4 Answers Coursera Quiz

Q8. If we are following the default convention in Django, which of the following column names would be used for a foreign key in table “abc” that is pointing to a primary key in table “xyz”?

  • xyz_id
  • id
  • abc_xyz_id
  • abc_id

Answer: xyz_id

These are Django Features and Libraries Week 4 Answers Coursera Quiz

See also  Web Application Technologies and Django | Week 1

Q9. If we are following the default convention in Django, which of the following column names would be used for a primary key in table “xyz” that is pointed to from a foreign key in table “abc”?

  • abc_id
  • abc_xyz_id
  • id
  • xyz_id

Answer: id

These are Django Features and Libraries Week 4 Answers Coursera Quiz

Q10. Which of the following model field types is used for a foreign key?

  • OneToManyKey
  • ForeignKey
  • OneToManyField
  • RemoteKey

Answer: ForeignKey

These are Django Features and Libraries Week 4 Answers Coursera Quiz

Q11. What does an “on_delete=models.CASCADE” clause imply in a Model field in Django?

  • Whenever a row is deleted from the table, the other rows are scanned to insure that the logical key is unique and any duplicates are removed.
  • When rows in a child table are deleted, the primary key of the corresponding row in the parent table is set to NULL.
  • When a row in the parent table is deleted, all the rows in a child table that point to that row via a foreign key are deleted.
  • Whenever a row is deleted, it is moved into a table named “CASCADE”.

Answer: When a row in the parent table is deleted, all the rows in a child table that point to that row via a foreign key are deleted.

These are Django Features and Libraries Week 4 Answers Coursera Quiz

Q12. When you add an index to a field in a database table, how are performance and storage affected?

  • Read performance is the faster, insert performance is faster, and extra storage is required
  • Read performance is faster, insert performance is slower, and extra storage is required
  • Read performance is faster, insert performance is the same, and no extra storage is required
  • Read performance is the same, insert performance is faster, and no extra storage is required
See also  Web Application Technologies and Django | Week 4

Answer: Read performance is faster, insert performance is slower, and extra storage is required

These are Django Features and Libraries Week 4 Answers Coursera Quiz

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These are Django Features and Libraries Week 4 Answers Coursera Quiz

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