Question

#travel expense = select sum(val) from expenses where type = 'travel';

#food expense = select sum(val) from expenses where type = 'food';

#phone expense = select sum(val) from expenses where type = 'phone';

#total expense = select sum(val) from expenses;

如何在一个查询中找到每笔费用的百分比？假设1000美元的总费用，其中50％用于食品，30％用于旅行，其余用于电话？

travel expense = (select sum(val) from expenses where type = 'travel')/(select sum(val) from expenses)*100 ==> What is the equivalent of this query in one query rather than two?

Answer 1

无法在“单个”查询中真正执行此操作，因为您需要每行和聚合数据来执行此操作，但是对于某些子查询，它将起作用：

SELECT ((
   SELECT SUM(val) FROM expenses WHERE type='travel'
) / (
   SELECT SUM(val) FROM expenses
)) AS pct

Answer 2

试试这个：

select type, sum(val) / (select sum(val) from expenses) * 100 Percentage
from expenses
group by type

结果：

+--------+------------+
|  TYPE  | PERCENTAGE |
+--------+------------+
| food   | 17.7778    |
| other  | 20         |
| phone  | 35.5556    |
| travel | 26.6667    |
+--------+------------+

这假设您需要表中所有费用的百分比。如果您想要过滤掉其他一些费用，请运行：

select type, sum(val) /
  (select sum(val) from expenses
   where type in ('travel', 'phone', 'food')) * 100 Percentage
from expenses
where type in ('travel', 'phone', 'food')
group by type

+--------+------------+
|  TYPE  | PERCENTAGE |
+--------+------------+
| food   | 22.2222    |
| phone  | 44.4444    |
| travel | 33.3333    |
+--------+------------+

Answer 3

你能做到：

SELECT type, COUNT(*) FROM expenses GROUP BY type WITH ROLLUP;

......然后从那里把它拉到一起？它确实提供了单个查询中所需的所有数据，即使您必须在查询之外做一些工作。

Answer 4

select
      PreAggregate.TotalExpenses,
      PreAggregate.TotalTravel,
      PreAggregate.TotalTravel / PreAggregate.TotalExpenses as PctForTravel,
      PreAggregate.TotalFood,
      PreAggregate.TotalFood / PreAggregate.TotalExpenses as PctForFood,
      PreAggregate.TotalPhone,
      PreAggregate.TotalPhone / PreAggregate.TotalExpenses as PctForPhone,
      PreAggregate.TotalExpenses,
      PreAggregate.ExpenseItems
   from
      ( select 
              sum( if( type = 'travel', val, 0 )) as TotalTravel,
              sum( if( type = 'food', val, 0 )) as TotalFood,
              sum( if( type = 'phone', val, 0 )) as TotalPhone,
              sum( val ) as TotalExpenses,
              count(*) as ExpenseItems
           from
              expenses
           where
              type in ( 'travel', 'food', 'phone' ) ) PreAggregate

在一个MySQL查询中查找结果

4 个答案: