使用SQL查询总和

Question

I have a table consisting of a department and income column. There are many entries in the table, each in a certain department and showing the income. I am trying to use MySQL to query the total SUM of income by department, and manipulating the results.

For instance, I want to show the (SUM of income of department A)divided by 2, (SUM of income of department B), and (SUM of income of department C)divided by 4.

I managed to find the sum of the total income of each department: SELECT Department,SUM(Income) AS income FROM School GROUP BY Department;

But how can I manipulate the sums so that I can divide by a different number for each department, and show the results? Any help would be appreciated.

Answer 1

You can use a CASE WHEN

SELECT Department ,
       SUM(case department when 'A' Income else 0 end)/2 AS income_A,
       SUM(case department when 'B' Income else 0 end)  AS income_B,
       SUM(case department when 'C' Income else 0 end)/4 AS income_C,
FROM School GROUP BY Department;

Answer 2

You can have one column called ModifiedIncome

SELECT 
Department,
SUM(Income),
CASE 
WHEN Department = 'A' THEN SUM(Income) / 2
WHEN Department = 'B' THEN SUM(Income)
WHEN Department = 'C' THEN SUM(Income) / 4
END
 AS ModifiedIncome FROM School GROUP BY Department;