postgresql - 错误：子查询在 PostgreSQL 中必须只返回一列

Question

我正在尝试编写一个需要 PostgreSQL 中的存储过程的 select 语句。但是，它因此错误而失败： ERROR: subquery must return only one column. 查询如下：

select(
(select 
'q1_parasiticide_carton_rebate' as rewardName,
case when  q1_parasiticide_carton_rebate is null then CAST(0 as VARCHAR)
else cast(coalesce(q1_parasiticide_carton_rebate,0) as VARCHAR(10)) end as rewardAmount
from temptable 
),
(select 
'q2_parasiticide_carton_rebate' as rewardName,
case when  q2_parasiticide_carton_rebate is null then CAST(0 as VARCHAR)
else cast(coalesce(q2_parasiticide_carton_rebate,0) as VARCHAR(10)) end as rewardAmount
from temptable
))
from temptable;

请帮我解决一下这个。