Question

我正在从子选择中选择一些东西，而这又是一个总和列表。现在我想选择base_unit列，其中包含度量单位。我似乎无法将base_unit添加到子选择中，因为它不适用于GROUP BY语句。

SELECT to_char(a.pow * f_unit_converter(base_unit, '[W]'), '000.00') 
FROM (
    SELECT sum (time_value) AS pow 
    FROM v_value_quarter_hour
    WHERE 
       mp_id IN (SELECT mp_id FROM t_mp WHERE mp_name = 'AC') AND 
       (now() - time_stamp < '5 day') 
    GROUP BY time_stamp
    ORDER BY time_stamp DESC 
) a 
LIMIT 1

我在哪里/如何从t_mp表中为每个总和选择base_unit，以便我可以将它传递给f_unit_converter函数？

非常感谢， MRB

Answer 1

假设您选择的所有行都具有相同的base_unit，您应该可以将其添加到您的SELECT 和 GROUP BY -query。

Answer 2

SELECT to_char(a.pow * f_unit_converter(a.base_unit, '[W]'), '000.00') 
FROM (
    SELECT sum (time_value) AS pow, t_mp.base_unit
    FROM v_value_quarter_hour
        inner join t_mp on (v_value_quarter_hour.mp_id = t_mp.mp_id)
    WHERE 
       t_mp.mp_name = 'AC' AND 
       (now() - time_stamp < '5 day') 
    GROUP BY time_stamp, base_unit
    ORDER BY time_stamp DESC 
) a 
LIMIT 1

Answer 3

使用INNER JOIN代替IN。像这样的东西

SELECT to_char(a.pow * f_unit_converter(base_unit, '[W]'), '000.00')  FROM (
    SELECT sum (time_value), base_unit AS pow 
    FROM v_value_quarter_hour
    INNER JOIN t_mp ON v_value_quarter_hour.mp_id = t_mp.mp_id
    WHERE mp_name = 'AC' AND 
       now() - time_stamp < '5 day'
    GROUP BY time_stamp, base_unit
    ORDER BY time_stamp DESC  ) a  LIMIT 1

从sum-sub-select中获取另一列

3 个答案: