Binning SQL data - sql

Question

Sorry if this has been asked before. Let's imagine I have table of temperature measurements inside a set of mechanical components:
ComponentID
Timestamp
Value
A
1st Jan 2020 00:00
20 C
A
1st Jan 2020 00:10
25 C
B
1st Jan 2018 00:00
19C
...and so on. Size of the table is fairly big, i.e. I have thousands of components with 10-minute measurements over a couple of years. What I need is a tally of the temperatures for each component in each year into, say, 5-degree bins, so a table looking like this:
ComponentID
Year
[-20;-15)
[-15,-10)
[-10;-5)
...
A
2018
5
20
300
...
A
2019
0
41
150
...
B
2018
60
10
1
...
..so for each component in each year, I count the number of measurements where the temperature has been in the [-20,-15) range, the number of measurements in the [-15,-10) range, and so on. I have a query doing this, but it's awfully slow. Is there an 'optimal' way of doing this kind of aggregation?

Answer 1

I'd say you should first pre-process your data to make it more simple to aggregate, then aggregate it with another query like (MySQL syntax):
SELECT cats.ComponentID, cats.Year,
SUM(tm5) `[-5;0)`,
SUM(t00) `[0;5)`,
SUM(tp5) `[5;10)`,
SUM(tp10) `[10;15)`,
SUM(tp15) `[15;20)`,
SUM(tp20) `[20;25)`,
SUM(tp25) `[25;30)`
FROM (
SELECT
ComponentID,
YEAR(`Timestamp`) `Year`,
(`Value` BETWEEN -5 AND -0.0001 ) tm5,
(`Value` BETWEEN 0 AND 4.9999 ) t00,
(`Value` BETWEEN 5 AND 9.9999 ) tp5,
(`Value` BETWEEN 10 AND 14.9999) tp10,
(`Value` BETWEEN 15 AND 19.9999) tp15,
(`Value` BETWEEN 20 AND 24.9999) tp20,
(`Value` BETWEEN 25 AND 29.9999) tp25
FROM
measurements
) cats
GROUP BY cats.ComponentID, cats.Year
ORDER BY cats.ComponentID, cats.Year
Inner query could be done into a temporary table if it's too much of a strain on memory.
I've ignored the fact that your temperatures are expressed as Strings including unit, which of course you should convert to numbers at some point, as it was not the point of the question.
Input (table named measurements):
id ComponentID Timestamp Value
------ ----------- ------------------- --------
3 B 2018-01-01 00:00:00 19
4 A 2019-03-05 05:10:00 16
5 A 2019-12-01 00:00:00 18
1 A 2020-01-01 00:00:00 20
2 A 2020-01-01 00:10:00 25
Result:
ComponentID Year [-5;0) [0;5) [5;10) [10;15) [15;20) [20;25) [25;30)
----------- ------ ------ ------ ------ ------- ------- ------- ---------
A 2019 0 0 0 0 2 0 0
A 2020 0 0 0 0 0 1 1
B 2018 0 0 0 0 1 0 0

Answer 2

I would suggest:
SELECT ComponentID, YEAR(`Timestamp`) as Year,
SUM(Value >= -20 AND Value < -15) as [-20;-15),
SUM(Value >= -15 AND Value < -10) as [-15;-10),
SUM(Value >= -10 AND Value < -5) as [-10;-05),
SUM(Value >= -5 AND Value < 0) as [-05;00),
SUM(Value >= 0 AND Value < 5) as [00;-05),
. . .
FROM measurements m
GROUP BY m.ComponentID, Year;
Note the use of inequalities to capture the exact ranges that you want.