CS 61A: Homework 9

Due by 11:59pm on Wednesday, 4/29


Download hw09.zip. Inside the archive, you will find a file called hw09.sql, along with a copy of the OK autograder.

Submission: When you are done, submit with python3 ok --submit. You may submit more than once before the deadline; only the final submission will be scored.

Using OK

The ok program helps you test your code and track your progress. The first time you run the autograder, you will be asked to log in with your @berkeley.edu account using your web browser. Please do so. Each time you run ok, it will back up your work and progress on our servers. You can run all the doctests with the following command:

python3 ok

To test a specific question, use the -q option with the name of the function:

python3 ok -q <function>

By default, only tests that fail will appear. If you want to see how you did on all tests, you can use the -v option:

python3 ok -v

If you do not want to send your progress to our server or you have any problems logging in, add the --local flag to block all communication:

python3 ok --local

When you are ready to submit, run ok with the --submit option:

python3 ok --submit

Readings: You might find the following references useful:

Table of Contents

To complete this homework assignment, you will need to use Sqlite version 3.8.3 or greater. See Lab 12 for setup and usage instructions.

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

sqlite3 -init hw09.sql

You should also check your work using ok:

python3 ok

If OK is not able to use sqlite3 to verify your work directly, OK will at least show you the output of the test cases, like the following:

size > Suite 1 > Case 1

Unfortunately, OK is unable to use sqlite3 to test your code directly.
Here is a transcript of what your code does in the sqlite3 interpreter.

    .read hw09.sql
    select name from size_of_dogs where size="toy" or size="mini";
EXPECTED (order does not matter):

Please manually check if your solution's output is correct.

As long as the displayed OUTPUT matches the EXPECTED output, your solution will be considered correct (even though OK will report a test failure).


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

create table parents as
  select "abraham" as parent, "barack" as child union
  select "abraham"          , "clinton"         union
  select "delano"           , "herbert"         union
  select "fillmore"         , "abraham"         union
  select "fillmore"         , "delano"          union
  select "fillmore"         , "grover"          union
  select "eisenhower"       , "fillmore";

create table dogs as
  select "abraham" as name, "long" as fur, 26 as height union
  select "barack"         , "short"      , 52           union
  select "clinton"        , "long"       , 47           union
  select "delano"         , "long"       , 46           union
  select "eisenhower"     , "short"      , 35           union
  select "fillmore"       , "curly"      , 32           union
  select "grover"         , "short"      , 28           union
  select "herbert"        , "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";

Instead of assuming that the dogs table has only the data above and writing

select "herbert";

The former query would still be correct if the name grover were changed to hoover or a row was added with the name harry.

Question 1

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 a 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

-- Example:
select name from size_of_dogs where size="toy" or size="mini";
-- Expected output:
--   abraham
--   eisenhower
--   fillmore
--   grover
--   herbert

Test your solution with OK:

python3 ok -q small

Question 2

Create a table by_height that has a column of the names of all dogs that have a parent, ordered by the height of the parent from tallest parent to shortest parent.
-- All dogs with parents ordered by decreasing height of their parent
create table by_height as

For example, fillmore has a parent (eisenhower) with height 35, and so should appear before grover who has a parent (fillmore) with height 32. The names of dogs with parents of the same height should appear together in any order. For example, barack and clinton should both appear at the end, but either one can come before the other.

-- Example:
select * from by_height;
-- Expected output:
--   herbert
--   fillmore
--   abraham
--   delano
--   grover
--   barack
--   clinton

Test your solution with OK:

python3 ok -q parent-height

Question 3

Create a single string for every pair of siblings that have the same size. Each value should be a sentence describing the siblings by their size, as shown in the expected output below.
-- Sentences about siblings that are the same size
create table sentences as

Each sibling pair should appear only once in alphabetical order.

-- Example:
select * from sentences;
-- Expected output:
--   barack and clinton are standard siblings
--   abraham and grover are toy siblings

Hint: First use a with clause to create a local table of siblings. Comparing the size of siblings will be simplified.

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.

Test your solution with OK:

python3 ok -q size-siblings

Question 4

When dogs are stacked on top of one another, the total height of the stack is the sum of the heights of the dogs.

Create a two-column table describing all stacks of dogs at least 170 cm high. The first column should contains a comma-separated list of dogs in the stack, and the second column should contain the total height of the stack. Order the stacks in increasing order of total height.

-- Ways to stack 4 dogs to a height of at least 170, ordered by total height
create table stacks as

A valid stack of dogs includes each dog only once, and the dogs should be listed in increasing order of height within the stack. Assume that no two dogs have the same height.

-- Example:
select * from stacks;
-- Expected output:
--   abraham, delano, clinton, barack|171
--   grover, delano, clinton, barack|173
--   herbert, delano, clinton, barack|176
--   fillmore, delano, clinton, barack|177
--   eisenhower, delano, clinton, barack|180

Hint: Use a with clause to create a recursive table with additional columns, such as the number of dogs that have been stacked and information about the last dog added (to control the dog order). Then, select the rows and columns from this larger table to generate the final solution.

Hint: Use height comparisons to ensure that dogs are not repeated in a stack.

Hint: Generating the comma-separated list of dogs is easier if your base case includes the name of one dog without any commas before or after it, rather than no dogs at all.

Test your solution with OK:

python3 ok -q stack

Question 5

Create a table tallest that includes the height and name of every dog that shares the 10's digit of its height with at least one other dog and has the highest 1's digit of all dogs that have the same 10's digit.

create table tallest as

-- Example:
select * from tallest;
-- Expected output:
--   28|grover
--   35|eisenhower
--   47|clinton

Explanation: grover is the tallest 20-something dog. eisenhower is the tallest 30-something dog. clinton is the tallest 40-something dog. barack is not included because there are no other 50-something dogs.

Test your solution with OK:

python3 ok -q tallest

Question 6

This question is optional but recommended for practice. You can receive full credit for the homework without attempting this problem.

A non-parent relation is either an ancestor that is not a parent (such as a grandparent or great-grandparent) or a descendent that is not a child (such as a grandchild or great-grandchild). Siblings are not relations under this definition.

Select all pairs that form non-parent relations ordered by the difference in height between one dog and the other.

-- All non-parent relations ordered by height difference
create table non_parents as

The shortest paired with the tallest should appear first, and the tallest paired with the shortest should appear last. If two pairs have the same height difference, they may appear together in any order.

-- Example:
select * from non_parents;
-- Expected output:
--   fillmore|barack
--   eisenhower|barack
--   fillmore|clinton
--   eisenhower|clinton
--   eisenhower|delano
--   abraham|eisenhower
--   grover|eisenhower
--   herbert|eisenhower
--   herbert|fillmore
--   fillmore|herbert
--   eisenhower|herbert
--   eisenhower|grover
--   eisenhower|abraham
--   delano|eisenhower
--   clinton|eisenhower
--   clinton|fillmore
--   barack|eisenhower
--   barack|fillmore

Test your solution with OK:

python3 ok -q relations