In the Excel sheet, I've compiled all 21 days' questions, totaling 84 questions (21 days * 4 questions per day). Each question includes solutions, provided in the LinkedIn post's comment box. I've also added a new column with YouTube links, so you can first learn the concept of each day's challenge before starting to solve the problem. These 84 questions cover SQL concepts from easy to advanced levels, making them excellent preparation for interviews.