USE tpch1;
set @a:=(select max(r_regionkey) from region);
select @a from region;
@a
4
4
4
4
4
select @a:=@a+1 from region;
@a:=@a+1
5
6
7
8
9
select @a, n_regionkey from nation order by 1,2;
@a	n_regionkey
9	0
9	0
9	0
9	0
9	0
9	1
9	1
9	1
9	1
9	1
9	2
9	2
9	2
9	2
9	2
9	3
9	3
9	3
9	3
9	3
9	4
9	4
9	4
9	4
9	4
select @a, n_regionkey from nation group by n_regionkey order by 1,2;
@a	n_regionkey
9	0
9	1
9	2
9	3
9	4
select @a:=@a+1, n_regionkey from nation group by 2 order by 2;
@a:=@a+1	n_regionkey
10	0
11	1
18	2
16	3
14	4
select @a:=@a+2 as c1, n_regionkey as c2, 1 as c3, '' as c4 from nation group by c2 order by 2;
c1	c2	c3	c4
16	0	1	
18	1	1	
32	2	1	
28	3	1	
24	4	1