Question

我被要求每个月显示一个月前N个计数记录的信息，我的意思是，我需要计算一个字段，选择前5个并与每个月/年绑定。我目前的代码如下：

( 
select calle1, count(calle1), year(fecha_registro), MONTH(fecha_registro) from dbo_accidentes1 
where year(fecha_registro)=2013 and MONTH(fecha_registro)=1 
GROUP BY calle1 
order by count(calle1) desc LIMIT 6 
) 
UNION 
( 
select calle1, count(calle1), year(fecha_registro), MONTH(fecha_registro) from dbo_accidentes1 
where year(fecha_registro)=2013 and MONTH(fecha_registro)=2 
GROUP BY calle1 
order by count(calle1) desc LIMIT 6 
) 
UNION 
( 
select calle1, count(calle1), year(fecha_registro), MONTH(fecha_registro) from dbo_accidentes1 
where year(fecha_registro)=2013 and MONTH(fecha_registro)=3 
GROUP BY calle1 
order by count(calle1) desc LIMIT 6 
) 
UNION 
( 
select calle1, count(calle1), year(fecha_registro), MONTH(fecha_registro) from dbo_accidentes1 
where year(fecha_registro)=2013 and MONTH(fecha_registro)=4 
GROUP BY calle1 
order by count(calle1) desc LIMIT 6 
) 
UNION 
( 
select calle1, count(calle1), year(fecha_registro), MONTH(fecha_registro) from dbo_accidentes1 
where year(fecha_registro)=2013 and MONTH(fecha_registro)=5 
GROUP BY calle1 
order by count(calle1) desc LIMIT 6 
) 
UNION 
( 
select calle1, count(calle1), year(fecha_registro), MONTH(fecha_registro) from dbo_accidentes1 
where year(fecha_registro)=2013 and MONTH(fecha_registro)=6 
GROUP BY calle1 
order by count(calle1) desc LIMIT 6 
)

它显示了一些像这样的东西：

https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-prn2/q71/s720x720/1468653_659639267414302_124224845_n.jpg

代码很大，但工作正常。我想知道是否有任何方法可以减少它，因为我认为我将来会与其他几个月合作。我尝试了很多连接，子查询，但它们都没有为我工作，我无法从内部查询或连接中的第二个表中检索前5条记录。

Answer 1

尝试这个，以防你的RDBMS支持窗口函数：

with t as 
(select calle1, count(calle1) as count_acc, year(fecha_registro) as year_acc, MONTH(fecha_registro) as Month_acc 
from dbo_accidentes1 
GROUP BY calle1, year(fecha_registro),MONTH(fecha_registro) ), 
t2 as
(select  calle1, count_acc, year_acc, Month_acc,
ROW_NUMBER() OVER (PARTITION BY calle1 ORDER BY count_acc desc) as rank)
select *
from t2
where rank <= 6

如何简化我的代码

1 个答案: