we started with the drchuck account and then let the program automatically pick the next two accounts to retrieve and add to our database the following is the first few rows in the people and follows tables after this run is completedpeople( 'drchuck' ( 'opencontent' ( 'lhawthorn' ( 'steve_coppin' ( 'davidkocher' rows follows( ( ( ( ( rows you can see the idnameand visited fields in the people table and you see the numbers of both ends of the relationship in the follows table in the people tablewe can see that the first three people have been visited and their data has been retrieved the data in the follows table indicates that drchuck (user is friend to all of the people shown in the first five rows this makes sense because the first data we retrieved and stored was the twitter friends of drchuck if you were to print more rows from the follows tableyou would see the friends of users and as well three kinds of keys now that we have started building data model putting our data into multiple linked tables and linking the rows in those tables using keyswe need to look at some terminology around keys there are generally three kinds of keys used in database model logical key is key that the "real worldmight use to look up row in our example data modelthe name field is logical key it is the screen name for the user and we indeed look up user' row several times in the program using the name field you will often find that it makes sense to add unique constraint to logical key since the logical key is how we look up row from the outside worldit makes little sense to allow multiple rows with the same value in the table primary key is usually number that is assigned automatically by the database it generally has no meaning outside the program and is only used to link rows from different tables together when we want to look up row in tableusually searching for the row using the primary key is the fastest way to find the row since primary keys are integer numbersthey take up very little storage and can be compared or sorted very quickly in our data modelthe id field is an example of primary key