get more fields from multiple things in sql - mysql

Question

I need to get multiple information within 1 query if possible.
Lets say this is the row:
Name - c1 - c2 - c3 - c4
What I need to get is the top in each column, so like
Paulus - 50 - 0 - 0 - 0
John - 0 - 50 - 0 - 0
Anne - 0 - 0 - 50 - 0
Chris - 0 - 0 - 0 - 50
And my query should return something like:
Paulus - c1 (50) - John - c2 (50) - Anne - c3 (50) - Chris - c4 (50)
Name - c1 - name - c2
I've tried: SELECT Name, c1, Name, c2 FROM table ORDER BY c1 DESC, c2 DESC
But it just doesn't work, I know it all looks vague but I hope someone is able to understand my question here...

Answer 1

you can create a store procedure or function and use a while loop then create a temp table in it and in each loop alter your table and add new column at the end return your answer.
but i recommend you to use another way to get your answer and change it in view. just change it for show to end-user.

Answer 2

You can do it with a subquery and series of self joins. A subquery will return the max numbers within the c1, ..., c4 columns. Then join your table 4x on the previous subquery to get the record(s) where c1, ..., c4 columns match the maximums.
However, pls heed #strawberry's advice and normalise your data structure.
I'll give you a sample code for 2 fields:
select t1.name as maxc1name, m.maxc1, t2.name as maxc2name, m.maxc2 from
(select max(c1) as maxc1, max(c2) as maxc2 from mytable) m
inner join mytable t1 on m.maxc1=t1.c1
inner join mytable t2 on m.maxc2=t2.c2
The catch: what happens if there is a tie in any of the columns and more than 1 record matches from your table any of the max values. You have not defined what you want to do with these, so I'm not dealing with it either.

Answer 3

Leaving the schema requirement as is, try:
create table `c_data` (
`Name` varchar(24) not null,
`c1` int(5) not null,
`c2` int(5) not null,
`c3` int(5) not null,
`c4` int(5) not null
);
insert c_data values
('Paulus', 50, 50, 0, 0),
('John', 0, 50, 0, 0),
('Anne', 0, 0, 50, 0),
('Chris', 0, 0, 0, 50);
select
name,
case greatest(c1, c2, c3, c4)
when c1 then concat('c1', ' (', c1, ')')
when c2 then concat('c2', ' (', c2, ')')
when c3 then concat('c3', ' (', c3, ')')
when c4 then concat('c4', ' (', c4, ')')
end as top_column
from c_data
order by name;
As #shadow states you still have to decide how to handle ties. This query just takes the first column with the shared max value (see Paulus).
BUT, consider normalizing your table as has been suggested. The data will be stored more efficiently and the table will be more versatile for future queries. Ties still need to be handled. This version takes the first data_type from an ascending alphanumeric sort.
create table c_data
(
name varchar(24),
data_type varchar(8),
data_value int(5)
);
insert into c_data values
('Paulus', 'c1', 50),
('Paulus', 'c2', 50),
('John', 'c2', 50),
('Anne', 'c3', 50),
('Chris', 'c4', 50);
select
name,
concat(min(data_type), ' (', max(data_value), ')') as top_column
from c_data
group by name
order by name;