i have a table in mySql like in this picture
and i want to write a query which result will group by LESSON column, and add new row which is average value of LESSON column and sum CNT column values....
for this query i use this one
i use this query but it gives result like in picture 3 and i cant sort by PERC in this case
select no, STUD_ID,CLASS,LESSON, AVG(PERC) as PERC,SUM(CNT) as CNT from t_lesson where LESSON='CHEM' group by CLASS union all select no,STUD_ID,CLASS,'AVERAGE' as LESSON, AVG(PERC) as PERC, SUM(CNT) as CNT from t_lesson where LESSON='CHEM' group by LESSON
It looks like you're selecting all of the rows where lesson is CHEM, and then you want an extra row with the average of the percantage. How about:
select * from ( -- this part gets all the "CHEM" rows select * from <your_table_name> where lesson = "CHEM" union -- this parts selects the aggregate row select NULL as `no`, NULL as `stud_id`, NULL as `class`, "average" as `lesson`, avg(percentage) as `perc`, sum(count) as `cnt` from <your_table_name> where lesson = "CHEM" ) q order by `perc` desc;
Note that the sorting is performed by the outer query.
don't know if you're looking for something like this:
SELECT fields_list, (field_to_modify + (SELECT AVG(average_field) FROM table2)) AS order_field FROM table1 WHERE your_conditions ORDER BY order_field;
