第一步：創建表及數據：

create table uid(uid int, --uidcate varchar(20), --類別price double --金額
)
insert into uid values(123,'c1',21);
insert into uid values(123,'c2',23);
insert into uid values(123,'c3',14);
insert into uid values(123,'c4',25);
insert into uid values(123,'c8',10);
insert into uid values(124,'c1',28);
insert into uid values(124,'c15',25);
insert into uid values(124,'c2',12);
insert into uid values(124,'c31',40);
insert into uid values(124,'c7',15);

查詢結果：

第二步：取uid的金額最多的前四名

1.獲取所有記錄

2.增加序列并過濾（增加序列需要排序）：

4.完成并查詢結果：

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