Find Total Time Spent by Each Employee Problem

Problem

Table: Employees

+-------------+------+
| Column Name | Type |
+-------------+------+
| emp_id      | int  |
| event_day   | date |
| in_time     | int  |
| out_time    | int  |
+-------------+------+

(emp_id, event_day, in_time) is the primary key (combinations of columns with unique values) of this table. The table shows the employees’ entries and exits in an office. event_day is the day at which this event happened, in_time is the minute at which the employee entered the office, and out_time is the minute at which they left the office. in_time and out_time are between 1 and 1440. It is guaranteed that no two events on the same day intersect in time, and in_time < out_time.

Write a solution to calculate the total time in minutes spent by each employee on each day at the office. Note that within one day, an employee can enter and leave more than once. The time spent in the office for a single entry is out_time - in_time.

Return the result table in any order.

The result format is in the following example.

Examples

Example 1:

Input: Employees table:

+--------+------------+---------+----------+
| emp_id | event_day  | in_time | out_time |
+--------+------------+---------+----------+
| 1      | 2020-11-28 | 4       | 32       |
| 1      | 2020-11-28 | 55      | 200      |
| 1      | 2020-12-03 | 1       | 42       |
| 2      | 2020-11-28 | 3       | 33       |
| 2      | 2020-12-09 | 47      | 74       |
+--------+------------+---------+----------+

Output:

+------------+--------+------------+
| day        | emp_id | total_time |
+------------+--------+------------+
| 2020-11-28 | 1      | 173        |
| 2020-11-28 | 2      | 30         |
| 2020-12-03 | 1      | 41         |
| 2020-12-09 | 2      | 27         |
+------------+--------+------------+

Explanation: Employee 1 has three events: two on day 2020-11-28 with a total of (32 - 4) + (200 - 55) = 173, and one on day 2020-12-03 with a total of (42 - 1) = 41. Employee 2 has two events: one on day 2020-11-28 with a total of (33 - 3) = 30, and one on day 2020-12-09 with a total of (74 - 47) = 27.

Solution

Method 1 - Group by

Code

SQL

select event_day as day, emp_id, sum(out_time - in_time) as total_time
from Employees
group by event_day, emp_id

We can also do:

select
    event_day as day, emp_id
    , sum(out_time) - sum(in_time) as total_time
from 
    Employees
group by 
    event_day, emp_id

Pandas

import pandas as pd

def total_time(employees: pd.DataFrame) -> pd.DataFrame:
    # Calculate the time spent for each entry
    employees['time_spent'] = employees['out_time'] - employees['in_time']
    
    # Group by emp_id and event_day, then sum the time_spent
    result_df = employees.groupby(['emp_id', 'event_day'])['time_spent'].sum().reset_index()
    result_df.rename(columns={'event_day': 'day', 'time_spent': 'total_time'}, inplace=True)
    
    return result_df

Problem#

Examples#

Solution#

Method 1 - Group by#

Code#

SQL#

Pandas#