MSSQL 字段分组拼接

方法1：缺点，不去重，不去空；见表1

with t  as(
  select 'A' parent, 'A1' child union all
  select 'A', 'A1' union all
  select 'A', '' union all
  select 'A', null union all
  select 'A', 'A2' union all
  select 'B', 'B1' union all
  select 'B', 'B2' union all
  select 'C', 'C1' union all
  select 'C', 'C2'
)
SELECT parent,
STUFF(
     (
      SELECT ','+ child FROM t a WHERE b.parent = a.parent FOR XML PATH('')
     ),1 ,1, '') children
FROM t b
GROUP BY parent

表1：

方法2：通过游标来处理，去重，去空。见表2

--定义游标并进行合并处理
declare @t table(parent varchar(100),child varchar(100))--定义结果集表变量
declare my_cursor cursor local for
with t1  as(
  select 'A' parent, 'A1' child union all
  select 'A', 'A1' union all
  select 'A', '' union all
  select 'A', null union all
  select 'A', 'A2' union all
  select 'B', 'B1' union all
  select 'B', 'B2' union all
  select 'C', 'C1' union all
  select 'C', 'C2'
)
select parent, child from t1 order by parent, child
declare @parent_old varchar(100) , @parent varchar(100) , @child varchar(100), @s varchar(100)
open my_cursor
fetch my_cursor into @parent , @child
select @parent_old = @parent , @s=''
while @@FETCH_STATUS = 0
begin
    if @parent = @parent_old
    begin
      if charindex(@child, @s)=0 and @child<>''
        select @s = @s + ',' + cast(@child as varchar)
    end else
      begin
        insert @t values(@parent_old , stuff(@s,1,1,''))
        select @s = ',' + cast(@child as varchar) , @parent_old = @parent
      end
    fetch my_cursor into @parent , @child
END
insert @t values(@parent_old , stuff(@s,1,1,''))
close my_cursor
deallocate my_cursor
select * from @t

表2：