sql錯誤（1242）：子查詢返回多於1行

Question

我有兩個表a_daily和o_daily_lcsgeneration ：

我正在嘗試此查詢：

update a_daily
set
  a_daily.Turbine_Generation =  
   (
     select sum(o_daily_lcsgeneration.Turbine_Generation) 
     from o_daily_lcsgeneration 
     where o_daily_lcsgeneration.Location = 1 
     group by o_daily_lcsgeneration.Date
  ) 

但收到上述錯誤，指出子查詢超過1行

Answer 1

刪除GROUP BY子句

UPDATE a_daily
SET a_daily.Turbine_Generation = 
(
        SELECT sum(o_daily_lcsgeneration.Turbine_Generation)
        FROM o_daily_lcsgeneration
        WHERE o_daily_lcsgeneration.Location = 1
)

它會使查詢返回不止一個具有多個日期的值。

更新1

UPDATE  a_daily a
        INNER JOIN
        (
            select g.Date, sum(g.Turbine_Generation) totalSum
            from o_daily_lcsgeneration g
            where g.Location = 1 
            group by g.Date
        ) b ON a.date = b.date
SET     a.Turbine_Generation = b.totalSum
WHERE       a.location = 1

要么

UPDATE  a_daily a
        LEFT JOIN JOIN
        (
            select g.Date, sum(g.Turbine_Generation) totalSum
            from o_daily_lcsgeneration g
            where g.Location = 1 
            group by g.Date
        ) b ON a.date = b.date
SET     a.Turbine_Generation = COALESCE(b.totalSum, 0)

Answer 2

運行子查詢，您將看到它返回多個行。 您正在按日期對結果進行分組，因此SUM表達式將計算每天的值。 您可以按照以下方式重新編寫查詢：

UPDATE a_daily
SET a_daily.Turbine_Generation = (SELECT SUM(o_daily_lcsgeneration.Turbine_Generation) 
                                    FROM o_daily_lcsgeneration 
                                   WHERE o_daily_lcsgeneration.Location = 1 
                                     AND o_daily_lcsgeneration.Date = 'YYYY-MM-DD'
                                GROUP BY o_daily_lcsgeneration.Date)

或（所有事件的總和）：

UPDATE a_daily
SET a_daily.Turbine_Generation = (SELECT SUM(o_daily_lcsgeneration.Turbine_Generation) 
                                    FROM o_daily_lcsgeneration 
                                   WHERE o_daily_lcsgeneration.Location = 1)

Answer 3

update a_daily
set
  a_daily.Turbine_Generation =  (
     select sum(o_daily_lcsgeneration.Turbine_Generation) 
     from o_daily_lcsgeneration where o_daily_lcsgeneration.Location = a_daily.Location  
     group by o_daily_lcsgeneration.Date
  )