Sorting issue with limit and offset MYSQL - mysql

Question

I am facing sorting issue in mysql
See the output of below query:
select astrologers.id,astrologers.name,chat_online,online,experience from `astrologers`
where `astrologers`.`status` = '1'
order by experience asc limit 10;
id
name
chat_online
online
experience
15
Astro Anoop
0
0
3
20
Test Astro2
0
0
3
3
Test anoop
0
0
5
4
Anoop Kumar trivedi
0
0
5
7
Test
0
0
5
58
Neeraj yadav
1
0
5
45
Satish Kumar Gupta
1
1
10
56
AP Sharma
1
0
15
40
VG Astrologer App
1
0
55
In above result id 58 (Neeraj yadav) is at 6th position but when I run the same query with limit 3, same id 58 (Neeraj yadav) is at 3rd position:
select astrologers.id,astrologers.name,chat_online,online,experience
from `astrologers`
where `astrologers`.`status` = '1'
order by experience asc limit 3;
id
name
chat_online
online
experience
20
Test Astro2
0
0
3
15
Astro Anoop
0
0
3
58
Neeraj yadav
1
0
5
The 3rd row in above result should be id 3 (Test anoop) but it gives id 58 (Neeraj yadav)
Is this bug in mysql?

Answer 1

Is this a bug in MySQL?
No. The problem is that your sort is not deterministic, and gives ties in the third position:
| 3 | Test anoop | 0 | 0 | 5 |
| 4 | Anoop Kumar trivedi | 0 | 0 | 5 |
| 7 | Test | 0 | 0 | 5 |
| 58 | Neeraj yadav | 1 | 0 | 5 |
All 4 users have the same experience, hence leaving the database to figure out how they should be sorted.
When asked to return to top 3 rows, the database picks the first two, and then one of the 4 ties. The result that you get might not be consistent over consequent executions of the same query, as you are starting to see.
Bottom line: know you data; if you want a deterministic result, then use a deterministic sort. We could, for example, use id to break the ties, hence making the result predictable:
order by experience, id limit 3