The construction company plans to **add more stations to the Yellow metro line**.

Our task is to determine the **total travel time for each metro line**. This information is crucial for the company to plan maintenance and expansion of the Yellow line without causing too much inconvenience to passengers.

To find the **total travel time**, we need to calculate the sum of travel times to each station using the `SUM()` function.





Calculating the sum of travel times to each station gives us the **time it takes for a train to travel from one end of the line to the other**. However, to find the **total turnaround time** (the time for a round trip), we need to **multiply this sum by 2**.

Note

Let's look at an **example** using a `metro_travel_time` table.

Suppose we want to find the **line with the most stations**.

SELECT line_name, COUNT(station_name) AS station_count
FROM metro_travel_time
GROUP BY line_name
ORDER BY station_count DESC

Let's return to the **task** because the workers **await our verdict** on the expansion of the metro station.

This course is perfect for those who already have a basic understanding of SQL and want to delve into more advanced concepts to craft more powerful queries. Throughout the course, you will become familiar with data grouping and filtering grouped data. You will also learn how to work with multiple tables simultaneously, including how to combine them. Additionally, you will explore different types of table joins and how to apply them in practice.

Challenge: Total Ride Time for Each Subway Line

Brief Instructions

解答