题目描述：按照id:vertex格式把所有行记录按照id从小到大合并到一行记录中。

数据如下表：

 预期结果如下图：

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解决方案：

方案一：基于游标

declare t_cur cursor  for select id,vertex from temp order by id;
declare @result varchar(max);
declare @id int;
declare @vertex varchar(10);
set @result = '';open t_cur;
fetch t_cur into @id,@vertex;
while(@@fetch_status = 0)
beginset @result = @result + cast(@id as varchar) + ':' + isnull(@vertex,'') + ',';fetch t_cur into @id,@vertex;
end
close t_cur;
deallocate t_cur;

方案二：一条SQL语句

declare @result varchar(max)
set @result = ''
select @result = @result + cast(id as varchar) + ':'+ isnull(vertex,'') + ','
from temp 
order by id--delete the last comma
set @result = substring(@result,1,len(@result)-1)
select @result

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结论：

       显然第二个解决方案的效率比第一个要高，但是就解决问题而言，如果能想到好的解决方案固然很好，如果想不到好的解决方案，游标至少是一种可行的解决方案。
If you can't find a good solution, then you should hug your "bad" one.

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参考:

[1]  T-SQL – How to select multiple rows into a single row