Troubleshooting - The general issue is that with ad-hoc queries, only the generic error "Error reading from database" is shown, and not the exact cause of the error, which would be some problem with the SQL query. Running the same query using DBeaver, (I had to find/replace { with ourprefix_ and } with a space)
I get the more helpful error message
SQL Error [1242] [21000]: Subquery returns more than 1 row
Commenting out all except the first subquery, I still got the error. So, there was an issue is with the first subquery.
Looking at the table ourprefix_feedback_value I saw that there are some entries where the name field with match
like '%Chapter%' but the typ field is not a textfield.
Assuming that this is what is causing the problem, I modified the query by adding an additional line in bold below
where
fc.timemodified = fc2.timemodified
and fi2.name like '%Chapter%'
and fi2.typ = 'textfield') as "Chapter name",
This also did not solve the issue. Then, checked the ourprefix_feedback_completed table looking for duplicates in the timestamps like
select fc3.timemodified, count(fc3.timemodified)
from
ourprefix_feedback_value fv3
left join vv_feedback_item fi3 on fi3.id = fv3.item
left join vv_feedback_completed fc3 on fc3.id = fv3.completed
where
fi3.name like '%Main%Script%'
GROUP BY fc3.timemodified
HAVING COUNT(fc3.timemodified) > 1
found 1646480361 was repeated twice. Two feedback items had exactly the same timestamp. Changed the second one to 1646480362 and the problem was solved.
