输出SQL中具有最大字段的行

Question

这是我拥有的数据表的一部分：

我如何查询该表以返回每个城市，仅返回具有MAX（turnover）的行，例如，对于Berlin，仅应返回具有21.574,00的行。

Answer 1

在Postgres上，您应该在此处使用DISTINCT ON：

SELECT DISTINCT ON (city) city, store, dow, turnover
FROM yourTable
ORDER BY city, turnover DESC;

Answer 2

要为每个max(turnover)生成city，请使用group by。

select city, max(turnover) turnover
from tableA
group by city

Answer 3

使用SELECT city, max(turnover) FROM table GROUP BY city这将返回城市及其最大营业额

Answer 4

如果您需要所有达到最大值的列，则可以使用像这样的窗口函数...

with your_fake_table as (
select * from (
values (1, 'Berlin' , 1 , 21000),
(1, 'Berlin' , 2 , 10000),
(1, 'Berlin' , 3 , 5000),
(2, 'Essen' , 31 , 10000),
(2, 'Essen' , 5 , 11000)
) as V (store, city, down, turnover))

select store, city, down, turnover
from (
select 
store,
city,
FIRST_VALUE(down) over (partition by city order by turnover desc) as down,
max(turnover) over (partition by city) as turnover
from your_fake_table
)V
group by store, city, down, turnover

但是如果您不需要向下列，则仅需要城市/商店/最大营业额一个简单的分组会更适合您]

select store, city, max(turnover) turnover
from your_table
group by store, city

请参见带有示例的小提琴演示：

https://dbfiddle.uk/?rdbms=postgres_12&fiddle=e61b775321b4120d87ea11626c09c140