Group by, converting rows to columns with no aggregate - mysql

Question

I need to group the table during my query, and up until know I was doing that after querying - with the code as my group is quite complicated. But with the new data it appears to take minutes, and I'm thinking is there better way.
My current query results in this:
FKId | Name | A | B | C
1 Alpha 2 3 2
1 Beta 2 5 7
2 Alpha 8 1 10
2 Beta 7 -5 6
2 Gamma 1 2 3
And I convert it to this:
FKId | Alpha[A] | Alpha[B] | Alpha[C] | Beta[A] | Beta[B] | Beta[C] | Gamma[A] | Gamma[B] | Gamma[C]
1 2 3 2 2 5 7
2 8 1 10 7 -5 6 1 2 3
Is it possible to do with SQL? (and I assume it should be much faster than if I do this with code)
The names can be anything
I have very big number of colums A, B, C (like 20 - 30). The number of result columns can easily go to thousands as average project has about 100 names.
I have like 10-20 columns that I should group by, but doing a single group by FKId is fine - these columns are the same.
We use different SQL DBs, so I cannot use specific functions like PIVOT. I know that we used MySQL, MsSQL and SQLite a lot
We use NHibernate if it makes any difference.
I would also honor the solution done for MySQL if specific functions are used. We use it in 80% and it will already greatly improve the average performance if I could do that at least for MySQL.

Answer 1

Basically, you want to transpose the data. Here is what you can try. It should work across all databases but you need to know the columns A, B, C, etc beforehand:
create table my_table (
fkid integer,
name varchar(10),
a integer,
b integer,
c integer
);
insert into my_table values(1,'alpha',2,3,2)
,(1,'beta',2,5,7)
,(2,'alpha',8,1,10)
,(2,'beta',7,-5,6)
,(2,'gamma',1,2,3);
select fkid
, max(case when name = 'alpha' then a else null end) as alphaa
, max(case when name = 'alpha' then b else null end) as alphab
, max(case when name = 'alpha' then c else null end) as alphac
, max(case when name = 'beta' then a else null end) as betaa
, max(case when name = 'beta' then b else null end) as betab
, max(case when name = 'beta' then c else null end) as betac
, max(case when name = 'gamma' then a else null end) as gammaa
, max(case when name = 'gamma' then b else null end) as gammab
, max(case when name = 'gamma' then c else null end) as gammac
from my_table
group by fkid;