Selecting multiple rows, where a difference in value is greater than x% - mysql

Question

I'm facing the following problem...
Given this data:
table : votes
=========
value
=========
10
25
38
90
92
93
98
100
120
I would like to return the value only, if the difference between next and previously accepted value is bigger than 10% of the first one:
if abs(int(a)-int(b))*100/int(a) < 10:
return True
So the end list should be (I have added % difference in square brackets):
==========
result
==========
10 ()
25 (150%)
38 (52%)
90 (136%)
100 (11%)
120 (20%)
The query should also sort those values first.
I'm able to do it with code (as shown above), but haven't got any chance in coming even close to a direct query.
MySQL v.8.0.19

Answer 1

You don't mention what version of MySQL you are using, so I'll assume it's a mordern one (8.x). You can use LAG(). For example:
select
concat('', value,
case when prev_value is null then ''
else concat('', 100 * (value - prev_value) / prev_value, '%')
end
) as result
from (
select
value,
lag(value) over (order by value) as prev_value
from t
) x
where prev_value is null or value > prev_value * 1.1
order by value

Answer 2

In MySQL 8.0, you can do this with lag(). Assuming that you want to sort rows by value, that would be:
select value
from (
select
value,
lag(value, 1, 0) over(order by value) lag_value
from mytable t
) t
where value > lag_value * 1.10
If you want to use an different ordering column, then you can change the order by clause to use the relevant column.
In earlier versions, one option is a correlated subquery:
select value
from mytable t
where value > 1.10 * coalesce(
(
select t1.value
from mytable t1
where t1.value < t.value
order by t1.value desc
limit 1
),
0
)
To use another ordering column here, you need to change the where clause and the order by clause of the subquery.
On the other hand, if you want to select the next row according to the ratio against the previously selected row, then that's a different question. You need some kind of iterative process: in SQL, one approach is a recursive query:
with
data as (
select value, row_number() over(order by value) rn
from mytable t
) d,
cte as (
select 1 is_valid, value, rn from data where rn = 1
union all
select
(d.value > 1.1 * c.value),
case when d.value > 1.1 * c.value then d.value else c.value end,
d.rn
from cte c
inner join data d on d.rn = c.rn + 1
)
select value from cte where is_valid order by value
The query enumerates the values, then walks the dataset sequentially while keeping track of the last selected value, and setting flags on records that should appear in the final resultset.