MYSQL选取每组数据第N条信息

MYSQL选取每组数据第N条信息

语句：主要采用变量的形式实现...

select contractno,outlet_code,rank from (  

select b.contractno,b.outlet_code,@rownum:=@rownum+1 ,  
if(@pdept=b.outlet_code,@rank:=@rank+1,@rank:=1) as rank,  
@pdept:=b.outlet_code  
from (  
select contractno,outlet_code from t_sale_customer_order_base order by outlet_code   
) b ,(select @rownum :=0 , @pdept := null ,@rank:=0) c ) result  
having rank =5 ;


select contractno from t_sale_customer_order_base where outlet_code='110101-000144';