MYSQL Sum of eatch row and limit to the best 15 - mysql

Question

I've this table : extended
+--------+-----+-----+-----+-----+- -+-----+-----+
| Name | T1 | T2 | T1 | T3 | .. | T19 | T20 |
+--------+-----+-----+-----+-----+- -+-----+-----+
| john | 5 | 10 | 50 | 10 | .. | 20 | 8 |
| bill | 2 | 8 | 11 | 5 | .. | 9 | 55 |
| james | 30 | 15 | 12 | 40 | .. | 13 | 10 |
| elsie | 28 | 35 | 20 | 32 | .. | 18 | 1 |
| .... | .. | .. | .. | .. | .. | .. | .. |
+--------+-----+-----+-----+-----+- -+-----+-----+
And i want to return this one :
+--------+-------+-----+-----+-----+-----+- -+-----+-----+
| Name | TOTAL | T1 | T2 | T1 | T3 | .. | T19 | T20 |
+--------+-------+-----+-----+-----+-----+- -+-----+-----+
| bill | 250 | 2 | 8 | 11 | 5 | .. | 9 | 55 |
| john | 230 | 5 | 10 | 50 | 10 | .. | 20 | 8 |
| elsie | 158 | 28 | 35 | 20 | 32 | .. | 18 | 1 |
| james | 129 | 30 | 15 | 12 | 40 | .. | 13 | 10 |
| .... | .... | .. | .. | .. | .. | .. | .. | .. |
+--------+-------+-----+-----+-----+-----+----+-----+-----+
Order by TOTAL. This total is the sum of best of 15 Tx ...
I don't now how to do this.
The table come from a request ( CREATE VIEW ) from another table with a lot of data.
Can you help me ?
At this point, i do the sum of ALL Tx, but it's not what i want ...
SELECT `Name`, (T1+T2+ T3+T4+T5+T6+T7+T8+T9+T10+T11+T12+T13+T14+T15+T16+T17+T18+T19+T20) AS TOTAL, T1,T2, T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15,T16,T17,T18,T19,T20
FROM `extended`
ORDER BY TOTAL DESC

Answer 1

If you wanted to remove the lowest value, that is easy:
select name,
(t1 + . . . + t20) -
least(t1, . . . , t20)
from table;
Unfortunately, MySQL does not have the nth function, so getting the second least and others is quite difficult.
If you had the values in separate rows, you could do:
select name, sum(t)
from (select en.*,
if(#name = name, #rn := #rn + 1, #rn := 1) as rn,
#name := name
from extended_norm en cross join
(select #name := '', #rn := 0) const
order by name, t desc
) en
where rn <= 15
group by name;
With your data structure, you'll probably need to write a user-defined function to do what you want.
EDIT:
If you want the list of t's, you can do it two ways. You can modify the above to include the pivot (this assumes that you have a column called something like tnumber to identify which t-value):
select name, sum(case when rn <= 15 then t end) as Total,
max(case when en.tnumber = 1 then t end) as T1,
max(case when en.tnumber = 2 then t end) as T2,
. . .
max(case when en.tnumber = 1 then t end) as T20
from (select en.*,
if(#name = name, #rn := #rn + 1, #rn := 1) as rn,
#name := name
from extended_norm en cross join
(select #name := '', #rn := 0) const
order by name, t desc
) en
group by name;
Otherwise, take the above query and join it to the denormalized table:
select e.*, tt.total
from extended e join
(the above query) tt
on e.name = tt.name;

Answer 2

It's awkward but this can also work!
select name, sum(t) from
(select name, t from (
select name, t1 as t from extended
union
select name, t2 as t from extended
union
select name, t3 as t from extended
union
select name, t4 as t from extended
union
select name, t5 as t from extended
union
select name, t6 as t from extended
union
select name, t7 as t from extended
union
select name, t8 as t from extended
union
select name, t9 as t from extended
union
select name, t10 as t from extended
union
select name, t11 as t from extended
union
select name, t12 as t from extended
union
select name, t13 as t from extended
union
select name, t14 as t from extended
union
select name, t15 as t from extended
union
select name, t16 as t from extended
union
select name, t17 as t from extended
union
select name, t18 as t from extended
union
select name, t19 as t from extended
union
select name, t20 as t from extended
) z
where name='bill' order by name, t desc limit 0,15);
But you have to run the query for each user by replacing 'bill' by other name