Why does adding a SUM(column) throw a group by error [SQL] - sql

Question

I found some similar questions, but none of the solutions would work, nor did they explain what was causing the issue.
I have a working query
SELECT pages.pageString pageName, timeSpent
FROM
(SELECT `page_id`, SUM(`time_spent`) as timeSpent
FROM `pageViews`
WHERE `time_spent` > 0
GROUP BY `page_id`) myTable
JOIN pages ON pages.id = page_id
ORDER BY timeSpent DESC
LIMIT 5
This returns results that look like
+------------------------------+-----------+
| pageName | timeSpent |
+------------------------------+-----------+
| page 1 | 394292 |
| page 2 | 66990 |
| page 3 | 53896 |
| page 4 | 37796 |
| page 5 | 14982 |
+------------------------------+-----------+
I'd like to add a column containing the percentage of timeSpent relative to the other pages, to start I added a SUM(timeSpent) to my query but that throws an error
In aggregated query without GROUP BY, expression #1 of SELECT list contains nonaggregated column 'pages.pageString'
Im not sure why this column is effected by adding this new column to the select statement.
Sadly any solution involving changing sql settings won't work due to company policy.
I appreciate any advice
UPDATE
The failing sql statement is
SELECT pages.pageString pageName, timeSpent FROM
(SELECT `page_id`, SUM(`time_spent`) as timeSpent FROM
`pageViews` WHERE `time_spent` > 0 GROUP BY `page_id`) myTable
JOIN pages ON pages.id = page_id ORDER BY timeSpent DESC LIMIT 5
As per the first answer I added a groupBy which solves the error
SELECT pages.pageString pageName, timeSpent, SUM(timeSpent) FROM
(SELECT `page_id`, SUM(`time_spent`) as timeSpent FROM `pageViews` WHERE `time_spent` > 0 GROUP BY `page_id`) myTable
JOIN pages ON pages.id = page_id GROUP BY pageName ORDER BY timeSpent DESC LIMIT 5
This however does not give the proper output
+------------------------------+-----------+----------------+
| pageName | timeSpent | SUM(timeSpent) |
+------------------------------+-----------+----------------+
| page 1. | 390210 | 390210 |
| page 2 | 66972 | 66972 |
| page3 | 52332 | 52332 |
| page4 | 25454 | 25454 |
| page5 | 13552 | 13552 |
+------------------------------+-----------+----------------+
Ideally this SUM(timeSpent) would be 390210+ 66972 + 52332 + 25454 + 13552 so that I may do timeSpent / SUM(timeSpent)

Answer 1

You did not say where you tried to put the sum(timeSpent) but I believe one can try to reconstruct with the error message:
In aggregated query without GROUP BY, expression #1 of SELECT list contains nonaggregated column 'pages.pageString'
It says what the problem is. You added sum(timeSpent) to the projection, but the SQL statement does not have a GROUP BY, in particular it mentions the first item which should be aggregated pages.pageString.
It would mention the other ones too, once you fix this one.
On the other hand, please make sure you post exactly the failing SQL statement instead of trying to describe how to get the error you have. It's better for us who try to help.
Update:
You have two tables/views pages and pageViews. The first one is used to get the page name. I would just focus on the time calculation to make things easier. Figuring out the name afterwards is simple, because it is directly connected to the page_id.
The first information you want is the sum of all times spent so that you can calculate the ratio to this sum.
This is simply an aggregation where you sum the times over all pages.
The second information you want is the sum of the times per page_id. You already know how to do that. You group by the page_id while aggregating the sums of each.
Try to put those two together now. You have the first statement of which the result shall be applied to each row of the second statement so that you get the table form page_id, time_spent_page, time_spent_all.
When you have step 3 then it is easy to add the page_name now, since you have the page_id which is required for a simple join.
I tried no to give away the solution. Maybe you like to try again following the steps above. If you have difficulties, simply leave a comment (maybe showing how far you got).
It might look complex in the beginning, but once you have done that successfully I hope you'll see that it can be simple.

Answer 2

Adding a column containing the percentage of timeSpent relative to the sum of all pages
SELECT pages.pageString pageName, timeSpent,
, timeSpent / sum(timeSpent) over() * 100 p
FROM
(SELECT `page_id`, SUM(`time_spent`) as timeSpent
FROM `pageViews`
WHERE `time_spent` > 0
GROUP BY `page_id`) myTable
JOIN pages ON pages.id = page_id
ORDER BY timeSpent DESC
LIMIT 5