Players

The 1901 Boston Americans (now Red Sox) Team

Problem to Solve

If you’re not familiar, baseball is a popular sport in which two teams of 9 players take turns batting (hitting a ball) and fielding (catching and throwing hit balls). Points (“runs”) are scored when a hitting team’s player hits a ball and eventually touches all bases before the fielding team’s players have the chance to get them “out.” Baseball is arguably most popular in the United States and Canada, where the MLB (Major League Baseball) has served as the professional association for players since 1876.

In a database called players.db, using a table called players, answer questions about MLB players who’ve played from 1871 to 2023.

Demo

Distribution Code

For this problem, you’ll need to download players.db, along with several .sql files in which you’ll write your queries.

$

wget https://cdn.cs50.net/sql/2024/x/psets/0/players.zip

unzip players.zip

rm players.zip

cd players

players/ $

ls

Schema

In players.db you’ll find a single table, players. In the players table, you’ll find the following columns:

• id, which uniquely identifies each row (player) in the table
• first_name, which is the first name of the player
• last_name, which is the last name of the player
• bats, which is the side (R for right or L for left) the player bats on
• throws, which is the hand (R for right or L for left) the player throws with
• weight, which is the player’s weight in pounds
• height, which is the player’s height in inches
• debut, which is the date (expressed as YYYY-MM-DD) the player began their career in the MLB
• final_game, which is the date (expressed as YYYY-MM-DD) the player played their last game in the MLB
• birth_year, which is the year the player was born
• birth_month, which is the month (expressed as an integer) the player was born
• birth_day, which is the day the player was born
• birth_city, which is the city in which the player was born
• birth_state, which is the state in which the player was born
• birth_country, which is the country in which the player was born

Specification

1. In 1.sql, write a SQL query to find the hometown (including city, state, and country) of Jackie Robinson.
2. In 2.sql, write a SQL query to find the side (e.g., right or left) Babe Ruth hit.
3. In 3.sql, write a SQL query to find the ids of rows for which a value in the column debut is missing.
4. In 4.sql, write a SQL query to find the first and last names of players who were not born in the United States. Sort the results alphabetically by first name, then by last name.
5. In 5.sql, write a SQL query to return the first and last names of all right-handed batters. Sort the results alphabetically by first name, then by last name.
6. In 6.sql, write a SQL query to return the first name, last name, and debut date of players born in Pittsburgh, Pennsylvania (PA). Sort the results first by debut date—from most recent to oldest—then alphabetically by first name, followed by last name.
7. In 7.sql, write a SQL query to count the number of players who bat (or batted) right-handed and throw (or threw) left-handed, or vice versa.
8. In 8.sql, write a SQL query to find the average height and weight, rounded to two decimal places, of baseball players who debuted on or after January 1st, 2000. Return the columns with the name “Average Height” and “Average Weight”, respectively.
9. In 9.sql, write a SQL query to find the players who played their final game in the MLB in 2022. Sort the results alphabetically by first name, then by last name.
10. In 10.sql, write SQL query to answer a question of your choice. This query should:
    • Make use of AS to rename a column
    • Involve at least condition, using WHERE
    • Sort by at least one column using ORDER BY

Usage

To test your queries as you write them in your .sql files, you can query the database by running

.read FILENAME

where FILENAME is the name of the file containing your SQL query. For example,

.read 1.sql

You can also run

$ cat FILENAME | sqlite3 players.db > output.txt

to redirect the output of the query to a text file called output.txt. (This can be useful for checking how many rows are returned by your query!)

How to Test

While check50 is available for this problem, you’re encouraged to instead test your code on your own for each of the following. If you’re using the players.db database provided in this problem’s distribution, you should find that…

• Executing 1.sql results in a table with 3 columns and 1 row.
• Executing 2.sql results in a table with 1 column and 1 row.
• Executing 3.sql results in a table with 1 column and 213 rows.
• Executing 4.sql results in a table with 2 columns and 2814 rows.
• Executing 5.sql results in a table with 2 columns and 12878 row.
• Executing 6.sql results in a table with 3 columns and 134 rows.
• Executing 7.sql results in a table with 1 columns and 1 row.
• Executing 8.sql results in a table with 2 columns and 1 row.
• Executing 9.sql results in a table with 2 columns and 516 rows.

10.sql is up to you!

Note that row counts do not include header rows that only show column names.

Correctness

check50 cs50/problems/2024/sql/players

How to Submit

In your terminal, execute the below to submit your work.

submit50 cs50/problems/2024/sql/players

Acknowledgements

Data retrieved and modified from github.com/chadwickbureau/baseballdatabank/tree/master, licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported License.