Q:

Is it faster or less memory intensive to limit data to one table in a database?

SQL databases are often organized by tables. These tables have the columns and rows that store information. Does it take significantly more time to change from table to table than it would to use only one table? I am considering storing each user as a different table. There will not be many users in the database. There would be a password column and a column for all of their owned appliances. Is this a bad practice? Also: what should I do instead of this? 
Potential duplicate: A seperate table for the posts which each user has liked - practical or not?
Reason it does not suit my needs: I do not know any alternatives to what I am doing.
Proposed database design          Traditional database design

Table: username123                 Table: login (only one table)
Password:       Appliances:        User:    Password:  Appliance1 ...
-----           -----              -----    -----      -----
-----           -----              -----    -----      -----
-----           -----              -----    -----      -----
        ...                                  ...

A:

Do not store each user as a different table!  This is a maintenance nightmare and hurts performance.
You cannot:

Query all users easily.
Set up foreign key relationships.
Modify the user table.
Easily optimize using indexes.
And the list goes on.

Because of the underlying structure of SQL, it is usually more efficient to put data into one large table rather than a zillion small tables.  
You have an entity called users.  You should have a table to represent that entity.

