Select Case FROM Union - sql

Question

In a purpose of reporting and creating report (MS SQL SERVER 2014) which will compare number of transactions and amounts from last day, same day last week and same day last month I need some query like this one, which is not working:
Select
Acquirer = case when Date = #Day then a.Acquirer
when Date = #LastWeekDay then b.Acquirer
when Date = #LastMonthDay then c.Acquirer
end
, RC = case when Date = #Day then a.RC
when Date = #LastWeekDay then b.RC
when Date = #LastMonthDay then c.RC
end
, Desc = case when Date = #Day then a.Desc
when Date = #LastWeekDay then b.Desc
when Date = #LastMonthDay then c.Desc
end
, Day_Tr_Count = case when Date = #Day then a.Count end
, LWD_Tr_Count = case when Date = #LastWeekDay then b.Count end
, LMD_Tr_Count = case when Date = #LastMonthDay then c.Count end
, Day_Tr_Amount = case when Date = #Day then a.Amount end
, LWD_Tr_Amount = case when Date = #LastWeekDay then b.Amount end
, LMD_Tr_Amount = case when Date = #LastMonthDay then c.Amount end
from
( select * from T1
union
select * from T2
union
select * from T3) x
group by Acquirer,RC,Desc
All 3 tables have pretty same structure:
T1,T2,T3(acquirer,RC,Desc,Count,Amount,Date).
Report should be:
result_table(Acquirer,RC,Desc,Daily_Count,Last_Week_Day_Count,Last_Month_Count,Daily_Amount,Last_Week_Day_Amount,Last_Month_Day_Amount)

Answer 1

Hmmm. You have an aggregation query with no group by. Perhaps:
Select v.Acquirer, v.RC, v.Desc,
Day_Tr_Count = sum(case when Date = #Day then a.Count end),
LWD_Tr_Count = sum(case when Date = #LastWeekDay then b.Count end),
LMD_Tr_Count = sum(case when Date = #LastMonthDay then c.Count end),
Day_Tr_Amount = sum(case when Date = #Day then a.Amount end
LWD_Tr_Amount = sum(case when Date = #LastWeekDay then b.Amount end),
LMD_Tr_Amount = sum(case when Date = #LastMonthDay then c.Amount end)
from (select * from T1
union all
select * from T2
union all
select * from T3
) x cross apply
(values (case when Date = #Day then a.Acquirer
when Date = #LastWeekDay then b.Acquirer
when Date = #LastMonthDay then c.Acquirer
end,
case when Date = #Day then a.RC
when Date = #LastWeekDay then b.RC
when Date = #LastMonthDay then c.RC
end,
case when Date = #Day then a.Desc
when Date = #LastWeekDay then b.Desc
when Date = #LastMonthDay then c.Desc
end
) v (Acquirer, RC, Desc)
group by v.Acquirer, v.RC, v.Desc;
Note: desc is a bad name for a column (or anything else). It is a SQL keyword (think order by).