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MySQL (C API)VC实例及代码下载 (1)(3)

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2016-06-13 10:06:331028browse


4.查询数据的最大排序问题(只能用一条语句写)

CREATE TABLE hard (qu char (11) ,co char (11) ,je numeric(3, 0))

insert into hard values ('A','1',3)

insert into hard values ('A','2',4)

insert into hard values ('A','4',2)

insert into hard values ('A','6',9)

insert into hard values ('B','1',4)

insert into hard values ('B','2',5)

insert into hard values ('B','3',6)

insert into hard values ('C','3',4)

insert into hard values ('C','6',7)

insert into hard values ('C','2',3)

要求查询出来的结果如下:

qu co je

----------- ----------- -----

A 6 9

A 2 4

B 3 6

B 2 5

C 6 7

C 3 4

就是要按qu分组,每组中取je最大的前2位!!

而且只能用一句sql语句!!!

select * from hard a where je in (select top 2 je from hard b where a.qu=b.qu order by je)

5.求删除重复记录的sql语句?

怎样把具有相同字段的纪录删除,只留下一条。

例如,表test里有id,name字段

如果有name相同的记录 只留下一条,其余的删除。

name的内容不定,相同的记录数不定。

有没有这样的sql语句?

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