數據庫基本腳本

CREATE TABLE `a` (

`ID` INT(10) NULL DEFAULT NULL,

`class` INT(10) NULL DEFAULT NULL,

`score` INT(10) NULL DEFAULT NULL

)

COLLATE='utf8_general_ci'

ENGINE=InnoDB;

insert into a values (1,1,110);

insert into a values (2,1,120);

insert into a values (3,1,130);

insert into a values (4,1,140);

insert into a values (5,2,210);

insert into a values (6,2,220);

insert into a values (7,2,230);

insert into a values (8,2,240);

insert into a values (9,3,310);

insert into a values (10,3,320);

insert into a values (11,4,410);

1.　對 class進行分組 取每組的前2條

select id,class,score,rank from (

select b.id,b.class,b.score,@rownum:=@rownum+1 ,

if(@pdept=b.class,@rank:=@rank+1,@rank:=1) as rank,

@pdept:=b.class

from (

select id,class,score from a order by id

) b ,(select @rownum :=0 , @pdept := null ,@rank:=0) c ) result

having rank <3 ;

rank <3 指的相當月ruwnum<3 每組都自動給上了序號.多少條記錄就多少個序號.指的是每組的.

2. ?對 class 進行分組 ? 取記錄滿足兩天的,也就是rownum=2 的數據

select id,class,score,rank from (

select b.id,b.class,b.score,@rownum:=@rownum+1 ,

if(@pdept=b.class,@rank:=@rank+1,@rank:=1) as rank,

@pdept:=b.class

from (

select id,class,score from a order by score desc

) b ,(select @rownum :=0 , @pdept := null ,@rank:=0) c ) result

having rank =2 ;

總結

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