fetch latest database entry that has a specific value

Question

I am currently developing a website for a friend and I ran into an issue that I am not able to solve to my satisfaction.

I was asked to log the user logins, and my approach was, to create a table that holds the columns:

• id
• user_id
• login_time
• login_ip

Now if the table lookes something like this:

id -- user_id -- login_time --------------- login_ip

1 ----- 1 --------- 2016-05-29 17:21:47 --- 11.0.0.1
2 ----- 1 --------- 2016-05-29 17:22:12 --- 11.0.0.1
3 ----- 2 --------- 2016-05-29 17:23:49 --- 11.0.0.1
4 ----- 3 --------- 2016-05-29 17:25:57 --- 11.0.0.1
5 ----- 2 --------- 2016-05-29 17:28:34 --- 11.0.0.1
6 ----- 1 --------- 2016-05-29 17:30:35 --- 11.0.0.1
7 ----- 3 --------- 2016-05-29 17:31:28 --- 11.0.0.1
8 ----- 3 --------- 2016-05-29 17:31:58 --- 11.0.0.1
9 ----- 2 --------- 2016-05-29 17:44:29 --- 11.0.0.1

How do I get the data from row 6 most efficiently? As this is the last time the user with "the user_id" of 1 logged in, is there a way to "ask" mysql to get the latest entry that has the "user_id = 1"?
My current approach would be

("SELECT * FROM login_tracking WHERE user_id = 1 ORDER BY id DESC LIMIT 1")

That is not a problem if tha database is small, but if it grows larger, it will be inefficient in my eyes.

Or would it be a better option to add the "login_time" and the "login_ip" to the users table and get the information from there, when the user last logged in and keep the same + the past login entries in the "login_tracking" table?

Answer 1

You´re original select is the best option:

select * from login_tracking where user_id = 1 order by id desc limit 1

But, be aware to create an index on both columns id and user_id:

create index two_cokumn_index on login_tracking (id , user_id );

This will really increase query performance.