mysql - sql 错误（1242）：子查询返回多于 1 行

Question

我有两张桌子a_daily和o_daily_lcsgeneration：

我正在尝试这个查询：

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
  ) 

但收到上述错误说子查询超过 1 行

Answer 1

删除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
)

它会导致查询返回多个日期的多个值。

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

或者

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

运行子查询，您会看到它返回不止一行。您按日期对结果进行分组，因此SUM表达式计算每天的值。您可以按如下方式重新编写查询：

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（所有事件的总和）：

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
  )