Merge two rows with a unique attribute

Question

This is a sample output of my table(time_entries)

user_name| entry_type   | entry_datetime
 User1   |   Time In    | 28-JUL-13  16:40:40
 User1   |   Time Out   | 28-JUL-13  16:40:41
 User2   |   Time In    | 28-JUL-13  16:41:13
 User2   |   Time Out   | 28-JUL-13  16:41:15
 User1   |   Time In    | 27-JUL-13  16:42:30
 User1   |   Time Out   | 27-JUL-13  16:42:34
 User2   |   Time In    | 27-JUL-13  16:43:32
 User2   |   Time Out   | 27-JUL-13  16:43:35

Now I used this query

SELECT te.user_name, te.entry_name, MAX(te.entry_datetime) AS date
FROM time_entries AS te
GROUP BY te.entry_type, te.user_name

and the result is this

user_name| entry_type   | entry_datetime
 User1   |   Time In    | 28-JUL-13  16:40:40
 User1   |   Time Out   | 28-JUL-13  16:40:41
 User2   |   Time In    | 28-JUL-13  16:41:13
 User2   |   Time Out   | 28-JUL-13  16:41:15

QUESTION: Is there a way to merge username with the same name in 1 line? and have an output something like this.

user_name|  Date     | Timein   | Timeout
User1    | 28-JUL-13 | 16:40:40 | 16:40:41
User2    | 28-JUL-13 | 16:41:13 | 16:41:15

I'm a little confuse how to do it.

Answer 1

I would approach it in this manner:

1. Create a query that returns the "time in" time for each user and date.
2. Create a query like #1 that returns the "time out" time for each user and date.
3. Merge the results together using LEFT JOIN.

The end result:

SELECT te.user_name, LEFT(te.entry_datetime, 10) AS entry_date, cin.entry_datetime AS timein, cout.entry_datetime AS timeout
FROM time_entries te
LEFT JOIN (SELECT user_name, LEFT(entry_datetime, 10) AS entry_date, MIN(entry_datetime) AS entry_datetime
    FROM time_entries
    WHERE entry_type = 'Time In'
    GROUP BY user_name, entry_date
) cin ON cin.user_name = te.user_name AND cin.entry_date = LEFT(te.entry_datetime, 9)
LEFT JOIN (SELECT user_name, LEFT(entry_datetime, 10) AS entry_date, MAX(entry_datetime) AS entry_datetime
    FROM time_entries
    WHERE entry_type = 'Time Out'
    GROUP BY user_name, entry_date
) cout ON cout.user_name = te.user_name AND cout.entry_date = LEFT(te.entry_datetime, 10)
GROUP BY te.user_name, entry_date;

Demo

Btw, I'm using LEFT() here because your column doesn't contain an actual date format that MySQL understands.