Homework 10: SQL

hw10.zip

Due by 11:59pm on Thursday, December 5

Instructions

Submission: When you are done, submit the assignment by uploading all code files you've edited to Gradescope. You may submit more than once before the deadline; only the final submission will be scored. Check that you have successfully submitted your code on Gradescope. See Lab 0 for more instructions on submitting assignments.

Using Ok: If you have any questions about using Ok, please refer to this guide.

Grading: Homework is graded based on correctness. Each incorrect problem will decrease the total score by one point. This homework is out of 2 points.

To check your progress, you can run sqlite3 directly by running:

python3 sqlite_shell.py --init hw10.sql

You should also check your work using ok:

python3 ok

Visualizing SQL

If you would like some support with visualizing SQL, please navigate to code.cs61a.org and select Start SQL Interpreter.

From there, you can either practice on tables you make yourself, existing tables from the CS 61A database (which can be found by typing .tables), or on the tables from the assignment you are working on by copying and pasting the entire CREATE TABLE ... command.

Required Questions

Getting Started Videos

These videos may provide some helpful direction for tackling the coding problems on this assignment.

To see these videos, you should be logged into your berkeley.edu email.

YouTube link

SQL

Dog Data

In each question below, you will define a new table based on the following tables.

CREATE TABLE parents AS
  SELECT "ace" AS parent, "bella" AS child UNION
  SELECT "ace"          , "charlie"        UNION
  SELECT "daisy"        , "hank"           UNION
  SELECT "finn"         , "ace"            UNION
  SELECT "finn"         , "daisy"          UNION
  SELECT "finn"         , "ginger"         UNION
  SELECT "ellie"        , "finn";

CREATE TABLE dogs AS
  SELECT "ace" AS name, "long" AS fur, 26 AS height UNION
  SELECT "bella"      , "short"      , 52           UNION
  SELECT "charlie"    , "long"       , 47           UNION
  SELECT "daisy"      , "long"       , 46           UNION
  SELECT "ellie"      , "short"      , 35           UNION
  SELECT "finn"       , "curly"      , 32           UNION
  SELECT "ginger"     , "short"      , 28           UNION
  SELECT "hank"       , "curly"      , 31;

CREATE TABLE sizes AS
  SELECT "toy" AS size, 24 AS min, 28 AS max UNION
  SELECT "mini"       , 28       , 35        UNION
  SELECT "medium"     , 35       , 45        UNION
  SELECT "standard"   , 45       , 60;

Your tables should still perform correctly even if the values in these tables change. For example, if you are asked to list all dogs with a name that starts with h, you should write:

SELECT name FROM dogs WHERE "h" <= name AND name < "i";

In other words, you should not assume that the dogs table has only the data in the table above by writing:

SELECT "hank";

The former query would still be correct if the name ginger were changed to gigi or a row was added with the name harry. Contrastingly, writing SELECT "hank"; would not.

Q1: By Parent Height

Create a table by_parent_height that has a column of the names of all dogs that have a parent, ordered by the height of the parent dog from tallest parent to shortest parent.

-- All dogs with parents ordered by decreasing height of their parent
CREATE TABLE by_parent_height AS
  SELECT "REPLACE THIS LINE WITH YOUR SOLUTION";

For example, finn has a parent ellie with height 35, and so should appear before ginger who has a parent finn with height 32. The names of dogs with parents of the same height should appear together in any order. For example, bella and charlie should both appear at the end, but either one can come before the other.

The by_parent_height table should look like this:

+----------+
| chil     |
+----------+
| hank     |
| finn     |
| ace      |
| daisy    |
| ginger   |
| bella    |
| charlie  |
+----------+

Use Ok to test your code:

python3 ok -q by_parent_height

Q2: Size of Dogs

The Fédération Cynologique Internationale classifies a standard poodle as over 45 cm and up to 60 cm. The sizes table describes this and other such classifications, where a dog must be over the min and less than or equal to the max in height to qualify as size.

Create a size_of_dogs table with two columns, one for each dog's name and another for its size.

-- The size of each dog
CREATE TABLE size_of_dogs AS
  SELECT "REPLACE THIS LINE WITH YOUR SOLUTION";

The size_of_dogs table should look like this:

+----------+----------+
| name     | size     |
+----------+----------+
| ace      | toy      |
| bella    | standard |
| charlie  | standard |
| daisy    | standard |
| ellie    | mini     |
| finn     | mini     |
| ginger   | toy      |
| hank     | mini     |
+----------+----------+

Use Ok to test your code:

python3 ok -q size_of_dogs

Q3: Sentences

There are two pairs of siblings that have the same size. Create a table that contains a row with a string for each of these pairs. Each string should be a sentence describing the siblings by their size.

-- [Optional] Filling out this helper table is recommended
CREATE TABLE siblings AS
  SELECT "REPLACE THIS LINE WITH YOUR SOLUTION";

-- Sentences about siblings that are the same size
CREATE TABLE sentences AS
  SELECT "REPLACE THIS LINE WITH YOUR SOLUTION";

Each sibling pair should appear only once in the output, and siblings should be listed in alphabetical order (e.g. "bella and charlie..." instead of "charlie and bella..."), as follows:

sqlite> SELECT * FROM sentences;
The two siblings, bella and charlie, have the same size: standard
The two siblings, ace and ginger, have the same size: toy

Hint: First, create a helper table containing each pair of siblings. This will make comparing the sizes of siblings when constructing the main table easier.

Hint: If you join a table with itself, use AS within the FROM clause to give each table an alias.

Hint: In order to concatenate two strings into one, use the || operator, e.g. SELECT "hello" || "world"; will return helloworld.

Use Ok to test your code:

python3 ok -q sentences

Q4: Low Variance

We want to create a table that contains the height range (defined as the difference between maximum and minimum height) of all dogs that share a fur type. However, we'll only consider fur types where each dog with that fur type is within 30% of the average height of all dogs with that fur type; we call this the low variance criterion.

For example, if the average height for short-haired dogs is 10, then in order to be included in our output, all dogs with short hair must have a height of at most 13 and at least 7 (inclusive).

Hint: MIN, MAX, and AVG will be useful here. Hint: You may want to first find the average height and make sure that:
* There are no heights smaller than 0.7 (i.e. 70%) of the average.
* There are no heights greater than 1.3 (i.e. 130%) of the average.

-- Height range for each fur type where all of the heights differ by no more than 30% from the average height
CREATE TABLE low_variance AS
  SELECT "REPLACE THIS LINE WITH YOUR SOLUTION";

Your output should have two columns, in this order: the fur type and the height_range for the fur types that meet this criteria. It should look like this:

+------------+--------------+
| fur        | height_range |
+------------+--------------+
| Curly      | 1            |
+------------+--------------+

The average height of long-haired dogs is 39.7, so the low variance criterion requires the height of each long-haired dog to be between 27.8 and 51.6. However, ace is a long-haired dog with height 26, which is outside this range. For short-haired dogs, bella falls outside the valid range (check!). Thus, neither short nor long haired dogs are included in the output. There are two curly haired dogs: finn with height 32 and hank with height 31. This gives a height range of 1.

Use Ok to test your code:

python3 ok -q low_variance

Submit Assignment

Submit this assignment by uploading any files you've edited to the appropriate Gradescope assignment. Lab 00 has detailed instructions.

Make sure to submit hw10.sql to the autograder!

Exam Practice

The following are some SQL exam problems from previous semesters that you may find useful as additional exam practice.