SQL Based Ranks

I am very new with SQL, and I am making a plugin to put on all servers on a bungee network to sync all the ranks across the servers, but I don't know how to do SQL. I have a table called Ranks that stores the username (TinyText), the coins they have (INT), and the rank they have (TinyText). It does have the auto increment id also. I'm a SQL NOOB! Help!