A user can have many interests. 
An interest can be interested to many users.
My database looks like that: 

```
Users table:
      id - primary key,
      name,
      email,

Interests table:
      id - primary key,
      title

Users_To_Interests table:
      id - primary key,
      user_id(id from users table)
      interest_id(id from interests table)

```

How can I improve **Users\_To\_Interests** table to be able to pick all users who have the same interest efficiently? **user\_id** and **interest\_id** columns don't have indexes or keys. If I need to add them, please show me how can I make that.

**Edition 1**: For example, 

```
user1 has interests : interest1, interest2, interest3;
user2 has interests : interest3, interest4;
user3 has interests : interest3, interest5;
user4 has interests : interest4;

If I want to get all users who have interest1, I should receive user1;
If I want to get all users who have interest2, I should receive user1;
If I want to get all users who have interest3, I should receive user1, user2, user3;

```