Homework 9:

Due by 11:59pm on Friday, April 24

Instructions

Download hw09.zip.

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. Check that you have successfully submitted your code on okpy.org. See Lab 0 for more instructions on submitting assignments.

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

Readings: You might find the following references useful:

Grading: Homework is graded based on correctness. Each incorrect problem will decrease the total score by one point. There is a homework recovery policy as stated in the syllabus. This homework is out of 2 points.

Usage

First, check that a file named sqlite_shell.py exists alongside the assignment files. If you don't see it, or if you encounter problems with it, scroll down to the Troubleshooting section to see how to download an official precompiled SQLite binary before proceeding.

You can start an interactive SQLite session in your Terminal or Git Bash with the following command:

python3 sqlite_shell.py

While the interpreter is running, you can type .help to see some of the commands you can run.

To exit out of the SQLite interpreter, type .exit or .quit or press Ctrl-C. Remember that if you see ...> after pressing enter, you probably forgot a ;.

You can also run all the statements in a .sql file by doing the following:

  1. Runs your code and then exits SQLite immediately afterwards.

    python3 sqlite_shell.py < lab13.sql
  2. Runs your code and then opens an interactive SQLite session, which is similar to running Python code with the interactive -i flag.

    python3 sqlite_shell.py --init lab13.sql

To complete this homework assignment, you will need to use SQLite version 3.8.3 or greater.

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

python3 sqlite_shell.py --init hw09.sql

You should also check your work using ok:

python3 ok

Questions (Required)

Dog Data

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.

Copy

Copy your code from hw08 for size_of_dogs to be able to more easily to do then next problems!

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 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, 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.

sqlite> select * from by_parent_height;
herbert
fillmore
abraham
delano
grover
barack
clinton

Use Ok to test your code:

python3 ok -q by_parent_height

Q2: 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.
-- Filling out this helper table is optional
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. "barack and clinton..." instead of "clinton and barack..."), as follows:

sqlite> select * from sentences;
abraham and grover are toy siblings
barack and clinton are standard siblings

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.

Use Ok to test your code:

python3 ok -q sentences

Submit

Make sure to submit this assignment by running:

python3 ok --submit

Troubleshooting/Advanced SQLite

Troubleshooting

Python already comes with a built-in SQLite database engine to process SQL. However, it doesn't come with a "shell" to let you interact with it from the terminal. Because of this, until now, you have been using a simplified SQLite shell written by us. However, you may find the shell is old, buggy, or lacking in features. In that case, you may want to download and use the official SQLite executable.

If running python3 sqlite_shell.py didn't work, you can download a precompiled sqlite directly by following the following instructions and then use sqlite3 and ./sqlite3 instead of python3 sqlite_shell.py based on which is specified for your platform.

Another way to start using SQLite is to download a precompiled binary from the SQLite website. The latest version of SQLite at the time of writing is 3.28.0, but you can check for additional updates on the website.

However, before proceeding, please remove (or rename) any SQLite executables (sqlite3, sqlite_shell.py, and the like) from the current folder, or they may conflict with the official one you download below. Similarly, if you wish to switch back later, please remove or rename the one you downloaded and restore the files you removed.

Windows

  1. Visit the download page linked above and navigate to the section Precompiled Binaries for Windows. Click on the link sqlite-tools-win32-x86-*.zip to download the binary.
  2. Unzip the file. There should be a sqlite3.exe file in the directory after extraction.
  3. Navigate to the folder containing the sqlite3.exe file and check that the version is at least 3.8.3:

    $ cd path/to/sqlite
    $ ./sqlite3 --version
    3.12.1 2016-04-08 15:09:49 fe7d3b75fe1bde41511b323925af8ae1b910bc4d

macOS Yosemite (10.10) or newer

SQLite comes pre-installed. Check that you have a version that's greater than 3.8.3:

    $ sqlite3
    SQLite version 3.8.10.2

Mac OS X Mavericks (10.9) or older

SQLite comes pre-installed, but it is the wrong version.

  1. Visit the download page linked above and navigate to the section Precompiled Binaries for Mac OS X (x86). Click on the link sqlite-tools-osx-x86-*.zip to download the binary.
  2. Unzip the file. There should be a sqlite3 file in the directory after extraction.
  3. Navigate to the folder containing the sqlite3 file and check that the version is at least 3.8.3:

    $ cd path/to/sqlite
    $ ./sqlite3 --version
    3.12.1 2016-04-08 15:09:49 fe7d3b75fe1bde41511b323925af8ae1b910bc4d

Ubuntu

The easiest way to use SQLite on Ubuntu is to install it straight from the native repositories (the version will be slightly behind the most recent release):

$ sudo apt install sqlite3
$ sqlite3 --version
3.8.6 2014-08-15 11:46:33 9491ba7d738528f168657adb43a198238abde19e