ケース選択FROM連合

Question

レポートとレポートの作成（MS SQL SERVER 2014）では、前月の最終日、先週の同じ日、先月の取引数と金額を比較し、このようなクエリが必要です。作業されていない。

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 

をすべての3つのテーブルはかなり同じ構造を持っている：

T1,T2,T3(acquirer,RC,Desc,Count,Amount,Date). 

報告書は次のようになります。

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。 group byの集約クエリがあります。おそらく：

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; 

注：descは、列（または何か他）のための悪い名前です。これはSQLキーワードです（考えてくださいorder by）。