如何选择对应行中前 5 个列的五个值？

Question

So I have two columns date and norder in my SQL table orders . We have to select dates with the top 10 maximum orders. We can do this like

SELECT date
FROM orders
ORDER BY norder DESC
LIMIT 10;

But we want to order these 10 dates such that the date is in descending order on values that have the same norder . How should we do this?

Answer 1

You can use window functions.

select a.date from 
(select date,dense_rank() over (order by norder desc) as rank
from orders
order by rank desc) as a
where rank <= 10
order by date desc;

This would give you the dates for the top 10 maximum orders (including dates for orders where the maximums are identical).

Answer 2

This should do.

SELECT date
FROM orders
ORDER BY order DESC, date DESC
LIMIT 10;

Answer 3

In Microsoft SQL Server:

SELECT TOP(10) [date]
FROM [orders]
ORDER BY [order] DESC, [date] DESC;