If you want to create tables for a database first you have to select the database. For selecting a database you have to enter the following query :
mysql> USE sample;
Database changed
Here sample is the database you want to select. The USE command dosen't need a semicolon at the end of the query.
You can use the following command to view the current database that you're connected to:
mysql> select database();
+------------+
| database() |
+------------+
| sample |
+------------+
Understand the difference between Use database and select database() as the former is selecting a database and the later one is displaying the currently selected one. After selecting the database you can create tables and other such operations.
Note : You have to select the database using the USE statement everytime you are entering into Mysql server or when you want to change the database.
If you type the following query you can see an information like Empty set (ie.,) there are no tables in the selected database.
mysql> show tables;
Empty set (0.00 sec)
| 
