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Primary Keys
A key defines and protects relationships between tables. A primary key is a special column that uniquely identifies records within a table. Each table can have one, and only one primary key.
The Primary Key Is Usually an ID
It's very common to have a column named id on each table in a database, and that id is the primary key for that table. No two rows in that table can share an id.
A PRIMARY KEY constraint can be explicitly specified on a column to ensure uniqueness, rejecting any inserts where you attempt to create a duplicate ID.
Assignment
Run the code. Notice that there's a bug: we have a violation of a PRIMARY KEY constraint on the id column. Fix the data that's being inserted.
When working with integer IDs, it's best practice to increment the id by 1 for each successive insert. Follow this convention when fixing the bug.