The objective of this challenge is to assess the ability to extract basic knowledge from a database. In the end, please submit documentation containing answers, the utilized source code, and explanations for the decisions made. Data cleaning and preparation are integral parts of this evaluation.
Read the data from the "database_challenge.xlsx" file in Excel format, which represents sales from an online store, and solve the following problems:
The store owner aims to gain a better understanding of the sources of their revenue. Create visualizations that assist in answering the following questions:
a) Who are the top customers of the store?
b) Which are the best-selling products in the store?
c) How does daily sales behavior look in terms of volume, revenue, and number of products sold?
d) How do different countries compare in terms of sales?
The store owner wishes to segment their customers more effectively for targeted marketing campaigns. Devise a solution to create three customer groups based on observed characteristics. Present the solution and justify your decisions.