How to make a separate column for each condition using one sql query?

I have a table with the data in the following format:

id    day    duration

1    Monday    15
1    Monday    17
1    Tuesday   20
1    Monday    8
2    Monday    9
3    Wednesday 11
...

It contains the number of seconds each user has watched tv on a specific day. One user can have more than one watching session per day. For example, user 1 has watched tv three times on Monday.

What I need to do is to create a separate column for each day, which will contain the total number of seconds watched on this day for each user. In other words, I need to have one row and seven columns for each user. The column would be: Monday, Tuesday, Wednesday, etc.

It would look like this:

id    Monday    Tuesday    Wednesday    ...
1       40         20          0
2       9          0           0
3       0          0           11

Right now, I can do that using the following script:

SELECT df.id, monday, tuesday, wednesday, thursday, friday, saturday, sunday
FROM 
    (
        SELECT id, SUM(duration) AS monday
        FROM data
        WHERE day = 'Monday'
        GROUP BY id
    ) AS df
    FULL JOIN
    (
        SELECT id, SUM(duration) AS tuesday
        FROM data
        WHERE day = 'Tuesday'
        GROUP BY id
    ) AS df1
    ON df.id = df1.id
    FULL JOIN
    (
        SELECT id, SUM(duration) AS wednesday
        FROM data
        WHERE day = 'Wednesday'
        GROUP BY id
    ) AS df2
    ON df.id = df2.id
    FULL JOIN
    (
        SELECT id, SUM(duration) AS thursday
        FROM data
        WHERE day = 'Thursday'
        GROUP BY id
    ) AS df3
    ON df.id = df3.id
    FULL JOIN
    (
        SELECT id, SUM(duration) AS friday
        FROM data
        WHERE day = 'Friday'
        GROUP BY id
    ) AS df4
    ON df.id = df4.id
    FULL JOIN
    (
        SELECT id, SUM(duration) AS saturday
        FROM data
        WHERE day = 'Saturday'
        GROUP BY id
    ) AS df5
    ON df.id = df5.id
    FULL JOIN
    (
        SELECT id, SUM(duration) AS sunday
        FROM data
        WHERE day = 'Sunday'
        GROUP BY id
    ) AS df6
    ON df.id = df6.id
)

The script does its job, but I’m pretty sure it’s not the most efficient way to do what I want. And I’m looking for a way to make this script better and shorter. I know that there definitely is a much simpler solution, but I don’t even know how to ask a question correctly.

Could anyone help me please or point to a similar question? I’d really appreciate it!

Answer

Use aggregation:

select id,
       sum(case when day = 'Monday' then duration end) as monday,
       sum(case when day = 'Tuesday' then duration end) as tuesday,
       . . . 
from data
group by id