Question

我有一个postgresql语句：

( select cast(start_time as date) as time , SUM(count) as  count 
from tbl_product  
where ( cast(start_time as date)  >= '2016-08-30 23:00:00'  and cast(start_time as date)  <= '2016-09-01 20:00:00' ) 
and ( extract(hour from start_time) >= 23  and extract(hour from start_time) <= 24)      
group by time order by time limit 5 )  

UNION ( select cast(start_time as date) as time , SUM(count) as  count 
from tbl_product  
where ( cast(start_time as date)  >= '2016-08-31 23:00:00'  and cast(start_time as date)  <= '2016-09-01 20:00:00' ) 
and ( extract(hour from start_time) >= 0  and extract(hour from start_time) < 20)      
group by time order by time limit 5 )

但由于UNION语句

，它返回同一日期的相同数据

time            count
date            numeric
"2016-08-31"    543595
"2016-08-31"    3666277
"2016-09-01"    3365093

如何添加以下数据值：

time            count
date            numeric
"2016-08-31"    4209872
"2016-09-01"    3365093

感谢您的帮助。

Answer 1

您需要将GROUP BY移出单个查询。这样的事情：

SELECT time, SUM(count) as  count FROM (
    ( select cast(start_time as date) as time , count 
    from tbl_product  
    where ( cast(start_time as date)  >= '2016-08-30 23:00:00'  and cast(start_time as date)  <= '2016-09-01 20:00:00' ) 
    and (extract(hour from start_time) >= 23))  
        UNION ALL
    ( select cast(start_time as date) as time , count 
    from tbl_product  
    where ( cast(start_time as date)  >= '2016-08-31 23:00:00'  and cast(start_time as date)  <= '2016-09-01 20:00:00' ) 
    and ( extract(hour from start_time) >= 0  and extract(hour from start_time) < 20))
    ) AS t
GROUP BY time ORDER by time;

我还将UNION更改为UNION ALL，因为在这种情况下似乎更有意义。最后，测试extract(hour from start_time) <= 24始终为真，因此它是多余的。

Answer 2

尝试此查询：

select
exe.time_,
sum(exe.count_)
from
(
    select cast(start_time as date) as time_ , SUM(count) as  count_ 
    from tbl_product  
    where ( cast(start_time as date)  >= '2016-08-30 23:00:00'  and cast(start_time as date)  <= '2016-09-01 20:00:00' ) 
    and ( extract(hour from start_time) >= 23  and extract(hour from start_time) <= 24)      
    group by time order by time limit 5   
    UNION 
    select cast(start_time as date) as time_, SUM(count) as  count_
    from tbl_product  
    where ( cast(start_time as date)  >= '2016-08-31 23:00:00'  and cast(start_time as date)  <= '2016-09-01 20:00:00' ) 
    and ( extract(hour from start_time) >= 0  and extract(hour from start_time) < 20)      
    group by time order by time limit 5 
) exe
group by exe.time_

如何统一相同的PostgreSQL数据

2 个答案: