Postgresql嵌套的聚合函数

我想查找在当月获得最大树叶数的员工。Postgresql嵌套的聚合函数

我开始与此查询：

select MAX(TotalLeaves) as HighestLeaves 
FROM (SELECT emp_id, count(adate) as TotalLeaves 
     from attendance 
     group by emp_id) AS HIGHEST;

但我面对显示雇员ID和获得的结果只会当月的问题。请帮助我。

来源

2013-11-01 Pooja

如果你只是想显示相应的雇员标识在当前的查询，您可以排序结果，并获得最高1行，你只需要当月组之前过滤数据得到：

select 
    emp_id, TotalLeaves 
from (
    select emp_id, count(adate) as TotalLeaves 
    from attendance 
    where adate >= date_trunc('month', current_date) 
    group by emp_id 
) as highest 
order by TotalLeaves desc 
limit 1;

其实，你并不需要在所有这里使用子查询：

select emp_id, count(adate) as TotalLeaves 
from attendance 
where adate >= date_trunc('month', current_date) 
group by emp_id 
order by TotalLeaves desc 
limit 1;

sql fiddle demo

来源

2013-11-01 08:53:30

谢谢你的回答。它确实有帮助。 – Pooja

我还有另一个查询。我有两个表：销售额（invoice_id，customer_id，sales_date，总金额）和发票（invoice_id，数量，价格，prod_id，total_amount）。我如何找到上周没有售出的产品？ – Pooja

@ user2944346我认为最好再问一个问题 –

SELECT emp_id, count(adate) as TotalLeaves 
    from attendance 
    where adata > date_trunc('month', NOW()) 
    group by emp_id 
    order by 2 desc limit 1

来源

2013-11-01 08:56:14 alexius

Postgresql嵌套的聚合函数

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