I am using **MySQl** database. 

I know if I create a **index** for a column, it will be fast to query data from a table by using that column index. But, I still have the following questions:

(suppose I have a table named **cars**, there is a column named *country*, and I have created index for *country* column)

1. I know for example the query `SELECT * FROM cars WHERE country='japan'`will use the index on column *country* to query data which is fast. How about `!=` operation? will `SELECT * FROM cars WHERE country!='japan';` also use index to query data?
2. Does `WHERE ... IN ...` operation use index to query data? For example `SELECT * FROM cars WHERE country IN ('japan','usa','sweden');`