Refactor level one to use city_name instead of name.
Refactor level two to use city_name instead of name.
Refactor level three to use city_name instead of name.
Refactor level 4 to use city_name instead of name.
Update level five

Change level text to reflect correct column name. Update errors to match new style
Refactor level six to use missile_id instead of id.
Refactor level seven to use missile_id instead of id.

Edit level seven text to reflect change. Edit level seven text to give more detail on primary
keys and autoincrementation.
Refactor level 8 to use missile_id.

Edit level text to reflect change in schema.
Refactor level nine to use missile_id and city_id.

Refactor answer to incorporate differentiated primary key columns. Edit
level text to match new schema.
Refactor level 10 to use city_id, missile_id, and city_name.
Refactor test suite and add coverage.
Touch up levels 6,8