Mysql:在group by中添加条件

Question

通过在查询中使用group by source子句，我得到以下结果。

Source  No_of_users
  1         2
  2         7
  3         3
  4         34
  5         21

如何对源的某些值进行分组，即输出，例如:

Source   No_of_users
  1+2         9
  3+5         24
  4           34

需要建议。

Answer 1

是的，像这样的联合:

SELECT SUM(no_of_users) AS some_sum from some_table where source in (1,2,3)
UNION
SELECT SUM(no_of_users) AS some_sum from some_table where source in (4,5,6)
UNION
SELECT SUM(no_of_users) AS some_sum from some_table where source in (6,7,8)