通过在sql中分组总计来计算最小值列

Question

I have a table named calcu

id  date       name     s1       s2      s3     s4       min_value
1   2/10/2017  dicky    7        4       8      9       [4]
2   2/10/2017  acton    12      15       17     19      [15]
3   2/10/2017  adney    28      13       19     10      [13]

If I total all fields in a single date then the result will be

    2/10/2017           47      32      44      38

Here minimum value is 32 . It means minimum value column is s2 . That's why I input s2 field value in min_value field in table calcu respectively.

I need how will I complete min_value field through SQL query?

I am using MYSQL database.

Plz show SQL query and query result.

Answer 1

You want to find the column with the minimum sum first and then use that column in your query. So you need a subquery where you compare each sum with the others and remember the column name. Then in the main query use that column name to check which value to show.

select 
  c.id, c.date, c.name, c.s1, c.s2, c.s3, c.s4, 
  case 
    when col.colname = 's1' then c.s1
    when col.colname = 's2' then c.s2
    when col.colname = 's3' then c.s3
    when col.colname = 's4' then c.s4
  end as min_value
from calcu c
cross join
(
  select
    case 
      when sum(s1) <= sum(s2) and sum(s1) <= sum(s3) and sum(s1) <= sum(s4) then 's1'
      when sum(s2) <= sum(s1) and sum(s2) <= sum(s3) and sum(s2) <= sum(s4) then 's2'
      when sum(s3) <= sum(s1) and sum(s3) <= sum(s2) and sum(s3) <= sum(s4) then 's3'
      else                                                                       's4'
    end as colname
  from calcu
) col;

The altered SQL fiddle: http://sqlfiddle.com/#!9/31579c/3