SQL Show Databse Query is for showing a list of Databses available on Database server. If you are using a GUI software to access your database (Query Analyser or PHPMYAdmin) then you will be able to see the list of avaialble databases in the software. But if you are using a Shell or Cosole (DOS) then to see list of available databses, the show databases query is useful.
Show database query is used to show all the databases on MYSQL Server. When you install a new mysql Server, by default it will come with one or two databases. That’s why if you use show database command, you will be able to see those databases.