Question

如何为MySQL生成此序列？
（N.B。： - 对于每个唯一对，重新生成序列）

1,1 - 1
1,1 - 2
1,1 - 3
1,2 - 1
1,2 - 2
1,3 - 1
1,4 - 1
1,4 - 2
1,4 - 3

Answer 1

创建表：-

create table dummy(id varchar(100));

在表中插入值：-

insert into dummy (id) values('1,1');    
insert into dummy (id) values('1,1');    
insert into dummy (id) values('1,1');    
insert into dummy (id) values('1,2');    
insert into dummy (id) values('1,2');    
insert into dummy (id) values('1,3');    
insert into dummy (id) values('1,4');    
insert into dummy (id) values('1,4');    
insert into dummy (id) values('1,4');

运行以下查询：-

select id,@aaaa:=ifnull(seq,@aaaa:=@aaaa+1)as seq from(select y.id,b,seq from (select 
id,@aaa:=@aaa+1 as b from dummy cross join (select @aaa:=0)a) as y  left join 
(select id,a,@aa:=@aa as seq from  (select * from (select id,@a:=@a+1 as a from dummy 
cross join (select @a:=0)a)as b group by id)a cross join (select @aa:=1)as d )
 as x on x.a=y.b) as z cross join  (select @aaaa:=0)a;

Answer 2

您需要SQL Server for MySQL中的cart.selectedItem函数

row_number

小提琴：http://sqlfiddle.com/#!9/ad4a0/3/0

在MySQL中为每个组生成序列

2 个答案: