MSSQL 使用临时表实现字符串合并处理

-->Title:Generating test data
-->Author:wufeng4552
-->Date :2009-09-30 15:16:26
if object_id('tb')is not null drop table tb
go
CREATE TABLE tb(col1 varchar(10),col2 int)
INSERT tb SELECT 'a',null
UNION ALL SELECT 'a',null
UNION ALL SELECT 'b',null
UNION ALL SELECT 'b',null
declare @col1 varchar(10)
declare @col2 int
update tb set @col2=case when @col1=col1 then @col2+1 else 1 end,
@col1=col1,col2=@col2

--每组 <=2 条的合并
select col1,
col2=ltrim(min(col2))+case when count(*)=1 then ''
else ','+ltrim(max(col2)) end
from tb group by col1
/*
col1 col2
---------- -------------------------
a 1,2
b 1,2

*/
--每组 <=3 条的合并
insert tb select 'b',3
select col1,
col2=CAST(MIN(col2) as varchar)
+CASE
WHEN COUNT(*)=3 THEN ','
+CAST((SELECT col2 FROM tb WHERE col1=a.col1 AND col2 NOT IN(MAX(a.col2),MIN(a.col2))) as varchar)
ELSE ''
END
+CASE
WHEN COUNT(*)>=2 THEN ','+CAST(MAX(col2) as varchar)
ELSE ''
END
from tb a group by col1
/*
col1 col2
---------- ---------------------
a 1,2
b 1,2,3

*/


if object_id('tempdb..#')is not null drop table #
go
select col1,
ltrim(col2)col2
into # from tb order by col1,col2
declare @col1 varchar(10)
declare @col2 varchar(20)
update # set @col2=case when @col1=col1 then @col2+','+col2 else col2 end,
@col1=col1,
col2=@col2
go
select col1,
max(col2)col2
from # group by col1
/*
col1 col2
---------- ------------
a 1,2
b 1,2,3

*/