row_number() OVER()

select * from tab

select   b,c,sum(d) e   from   tab  group   by   b,c  -- 先根据b分 再根据c分

SELECT b, c, d,
SUM(d) OVER(PARTITION BY b,c ORDER BY d) e FROM tab

SELECT b, c, d,
SUM(d) OVER(PARTITION BY b,c ) e FROM tab

 --为什么将 ORDER BY 拿掉就是这个样子？

select row_number() OVER(order by getdate())
--row_number() 必须跟 OVER() 还有 order by一起连用

 select *,  row_number() OVER(order by D) from tab