Problem to Solve

The CS50 Duck has been stolen! The town of Fiftyville has called upon you to solve the mystery of the stolen duck. Authorities believe that the thief stole the duck and then, shortly afterwards, took a flight out of town with the help of an accomplice. Your goal is to identify:

  • Who the thief is,
  • What city the thief escaped to, and
  • Who the thief’s accomplice is who helped them escape

All you know is that the theft took place on July 28, 2023 and that it took place on Humphrey Street.

How will you go about solving this mystery? The Fiftyville authorities have taken some of the town’s records from around the time of the theft and prepared a SQLite database for you, fiftyville.db, which contains tables of data from around the town. You can query that table using SQL SELECT queries to access the data of interest to you. Using just the information in the database, your task is to solve the mystery.


Getting Started

For this problem, you’ll use a database provided to you by CS50’s staff.

Download the distribution code

Log into, click on your terminal window, and execute cd by itself. You should find that your terminal window’s prompt resembles the below:


Next execute


in order to download a ZIP called into your codespace.

Then execute


to create a folder called fiftyville. You no longer need the ZIP file, so you can execute


and respond with “y” followed by Enter at the prompt to remove the ZIP file you downloaded.

Now type

cd fiftyville

followed by Enter to move yourself into (i.e., open) that directory. Your prompt should now resemble the below.

fiftyville/ $

Execute ls by itself, and you should see a few files:

answers.txt  fiftyville.db  log.sql

If you run into any trouble, follow these same steps again and see if you can determine where you went wrong!


For this problem, equally as important as solving the mystery itself is the process that you use to solve the mystery. In log.sql, keep a log of all SQL queries that you run on the database. Above each query, label each with a comment (in SQL, comments are any lines that begin with --) describing why you’re running the query and/or what information you’re hoping to get out of that particular query. You can use comments in the log file to add additional notes about your thought process as you solve the mystery: ultimately, this file should serve as evidence of the process you used to identify the thief!

As you write your queries, you may notice that some of them can become quite complex. To help keep your queries readable, see principles of good style at The indentation section may be particularly helpful!

Once you solve the mystery, complete each of the lines in answers.txt by filling in the name of the thief, the city that the thief escaped to, and the name of the thief’s accomplice who helped them escape town. (Be sure not to change any of the existing text in the file or to add any other lines to the file!)

Ultimately, you should submit both your log.sql and answers.txt files.



  • Execute sqlite3 fiftyville.db to begin running queries on the database.
    • While running sqlite3, executing .tables will list all of the tables in the database.
    • While running sqlite3, executing .schema TABLE_NAME, where TABLE_NAME is the name of a table in the database, will show you the CREATE TABLE command used to create the table. This can be helpful for knowing which columns to query!
  • You may find it helpful to start with the crime_scene_reports table. Start by looking for a crime scene report that matches the date and the location of the crime.
  • See this SQL keywords reference for some SQL syntax that may be helpful!

How to Test


check50 cs50/problems/2024/spring/fiftyville

How to Submit

  1. Download your log.sql and answers.txt files by control-clicking or right-clicking on the files in your codespace’s file browser and choosing Download.
  2. Go to CS50’s Gradescope page.
  3. Click Problem Set 7: Fiftyville.
  4. Drag and drop your log.sql and answers.txt files to the area that says Drag & Drop. Be sure they have those exact filenames! If you upload a file with a different name, the autograder likely will fail when trying to run it, and ensuring you have uploaded files with the correct filenames is your responsibility!
  5. Click Upload.

You should see a message that says “Problem Set 7: Fiftyville submitted successfully!” You may not see a score just yet, but if you see the message then we’ve received your submission!


Inspired by another case over at SQL City.