參考地址：https://blog.csdn.net/weixin_39358657/article/details/89644822
通用模板：
select a.*
from ( select t1.*,(select count(*)+1 from 表 where 分組字段=t1.分組字段 and 排序字段<t1.排序字段) as group_id from 表 t1 ) a where a.group_id<=3 # 假設取前3條
舉個栗子：
數據准備：
CREATE TABLE Score( s_id VARCHAR(20) COMMENT '學生編號', c_id VARCHAR(20) COMMENT '課程編號', s_score INT(3) COMMENT '分數', PRIMARY KEY(s_id,c_id) )ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT '成績表'; -- 成績表測試數據 insert into Score values('01' , '01' , 80); insert into Score values('01' , '02' , 90); insert into Score values('01' , '03' , 99); insert into Score values('02' , '01' , 70); insert into Score values('02' , '02' , 60); insert into Score values('02' , '03' , 80); insert into Score values('03' , '01' , 80); insert into Score values('03' , '02' , 80);
需求：查詢每門功課成績最好的前兩名
需求分析：相當於查詢課程為‘01’的前兩名，課程為‘02’的排名前兩名......
套用模板：
select a.s_id,a.c_id,a.s_score,a.group_id from ( select t1.*,(select count(*)+1 from score where c_id=t1.c_id and s_score>t1.s_score) as group_id from score t1 ) a where a.group_id<=2 ORDER BY c_id asc,group_id asc;
結果：
補充：
此處也可以使用下面的查詢語句（前提是課程不多）
SELECT *FROM (SELECT a.s_id,a.c_id,a.s_score, @i:=@i+1 as 排名 FROM score a,(SELECT @i:=0)b WHERE a.c_id='01' ORDER BY a.s_score DESC ) c WHERE 排名 BETWEEN 1 AND 2 UNION SELECT *FROM (SELECT a.s_id,a.c_id,a.s_score, @j:=@j+1 as 排名 FROM score a,(SELECT @j:=0)b WHERE a.c_id='02' ORDER BY a.s_score DESC ) c WHERE 排名 BETWEEN 1 AND 2 UNION SELECT *FROM (SELECT a.s_id,a.c_id,a.s_score, @k:=@k+1 as 排名 FROM score a,(SELECT @k:=0)b WHERE a.c_id='03' ORDER BY a.s_score DESC ) c WHERE 排名 BETWEEN 1 AND 2
上面的查詢語句使用了變量@變量名：。
select @i:=@i+1 相當於對每一行進行添加序號；SELECT @i:=0設置初始值為0。