是否可以编写一个将sum（amount）分类为2列的查询？

Question

我有像这样的MyTbl

Id  type    amount
--  ----    ------
1   1       100
2   1       200
3   2       300
4   2       400

是否可以在Android中为sqlite编写一个返回此查询？

Amount1 Amount2
------- -------
300     700

我写了以下查询，但不行：

select SUM(a.amount) as Amount1, SUM(b.amount) as Amount2 from MyTbl a inner join MyTbl b
on a.id = b.id
group by a.type

它返回：

Amount1 Amount2
------- -------
300     300
700     700

Answer 1

SELECT
    SUM(CASE WHEN type = 1 THEN amount ELSE 0 END) amount1,
    SUM(CASE WHEN type = 2 THEN amount ELSE 0 END) amount2
FROM MyTbl

SQL FIDDLE