select * from AAA a where not exists (select 1 from AAA where PN=a.PN and QTY>a.QTY)

------解决方案--------------------
SQL code
select * from aaa t where qty=(select max(qty) from tb where pn=t.pn)

------解决方案--------------------
SQL code
select * from aaa a where not exists
(select 1 from aaa where PN=a.PN and QTY>a.QTY)

------解决方案--------------------
SQL code
create table AAA([USER] varchar(10),PN varchar(20),QTY int)
insert into AAA select 'O-10','306-077A',757
insert into AAA select 'O-16','306-077A',127
insert into AAA select 'G-42','306-077A',20
insert into AAA select 'B-40','306-179',12
insert into AAA select 'F-58','306-179',120
insert into AAA select 'H-23','306-224',50
go
select * from AAA a where not exists(select 1 from AAA where PN=a.PN and QTY>a.QTY)
/*
如果同一客户采购不止一笔,则要先统计后再比较:
;with cte as(
select [USER],PN,sum(QTY)as QTY from tb group by [USER],PN
)select * from cte a where not exists(select 1 from cte where PN=a.PN and QTY>a.QTY)
*/
go
drop table AAA
/*
USER       PN                   QTY
---------- -------------------- -----------
O-10       306-077A             757
F-58       306-179              120
H-23       306-224              50

(3 行受影响)
*/