Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_7 (company VARCHAR, principal_activities VARCHAR)

### Question ###
What company focuses on Engine Overhaul for their principal activity?

### Accurate SQL ###

SELECT company FROM table_name_7 WHERE principal_activities = "engine overhaul"