Result from mysql find_in_set is not correct

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Hello,

I have an issue that the mysql query result is incorrect, that is instead of 1,2,3 it return 1,2,4

Values in Table are as:

id  academic_year_id	class_id	avg_grade_point
1	   6	          1	         4.0
2	   6              1          4.13
3	   6              1          4.25
4	   6              1          4.0
5	   6              1          4.13

Please help.

What I have tried:

SQL

SELECT id, avg_grade_point, FIND_IN_SET( avg_grade_point, 
                ( SELECT GROUP_CONCAT( avg_grade_point ORDER BY avg_grade_point DESC )
                FROM final_results WHERE academic_year_id = 6 AND class_id = 1  ) ) AS rank 
                FROM final_results 
                WHERE academic_year_id = 6 AND class_id = 1

Posted 19-Feb-21 1:52am

nyt1972

Updated 19-Feb-21 3:24am

v3

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CHill60 · Answer 1 · 2021-02-19T03:24:00

Follow @OriginalGriff's excellent advice and run the query

SQL

SELECT GROUP_CONCAT( avg_grade_point ORDER BY avg_grade_point DESC )
                FROM final_results WHERE academic_year_id = 6 AND class_id = 1

You will see the results

4.25,4.13,4.13,4.00,4.00

So you have a "joint second" placing with 4.13. That means there is no "third place" to award, it jumps straight to fourth. If you add in an extra line of data e.g.

(6,6,1,3.13);

you only get rankings 1,2,4 and 6 because there is also a tied place scenario with 4.00

I think you are getting confused between Rank and Row Number. This article might help to explain it better Similarities and Differences among RANK, DENSE_RANK and ROW_NUMBER Functions – {coding}Sight[^]

OriginalGriff · Answer 2 · 2021-02-19T02:22:00

Either your query is not as shown, or your data isn't: runnin that query on that data will give you no rows returned even if we assume that academic_year is actually academic_year_id and class_d is actually class_id
Why not? Because there are no rows in your data which match the condition:

SQL

WHERE academic_year_id = 6

All your rows contain "1", not "6".

So start by looking closely at your tables and the data they contain; then run your query in parts to find out exactly what each returns before "bolting them together" with FIND_IN_SET

Result from mysql find_in_set is not correct

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