a design about cache(using redis) , and some problem about it

Now, Let's look at the following scenario: A website manage 10,000 students, and show top 100 of student's achievement. I use mysql storage every student personal information(name email sex and achievement) but I have to get every student achievement and caculate Top 100, so I use redis to solve

a question about redis cache

Let's look at the following scenario: A website has 1 player, to make question easier, I use mysql storage player with just one table: "player_table" --table here- name string score int now, I want to show Top 100 of those players by socre. if only with mysql, I have to caculate Top