【原】一道SQL题(根据一个字段值的变化，在另一个字段中计数)

题目如下：

if object_id('[tb]') is not null drop table [tb]

go

create table [tb]([value1] int,[value2] int)

insert [tb]

select 1,12 union all

select 1,13 union all

select 1,23 union all

select 0,14 union all

select 0,15 union all

select 1,16 union all

select 0,23 union all

select 0,22 union all

select 1,21 union all

select 1,12

要求显示的结果:

value1 value2 col3

----------- ----------- -----------

1 12 1

1 13 2

1 23 3

0 14 1

0 15 2

1 16 1

0 23 1

0 22 2

1 21 1

1 12 2

****************************************

我的做法：

****************************************

declare @value1 as int,@value2 as int;

declare @prvvalue1 as int,@flag as int;

declare @result table

(

value1 int,

value2 int,

col3 int

);

declare c cursor fast_forward for

select value1,value2

from tb;

open c

fetch next from c into @value1,@value2;

select @prvvalue1 = @value1,@flag = 0;

while @@FETCH_STATUS = 0

begin

if @value1 <> @prvvalue1

select @prvvalue1 = @value1,@flag = 0;

set @flag = @flag + 1;

insert into @result values(@value1,@value2,@flag);

fetch next from c into @value1,@value2;

end

close c;

deallocate c;

select *

from @result;