茴香豆的n种写法之③——sql更新id的n种写法

此解法来自博客园思想瞭望者开设之“sql精英群”对话。

iceline(43417365) 11:36:59

 

现在PATH的上下级关系是对了，我如何更新parentID

thanks(305380844) 12:54:12
做出来了，试试
update test set parentid = b.parentidb
from test ,(
select a.id, a.parentid, a.path , b.id as parentidb, b.path as bpath
from test a cross join test b
where len(REPLACE(a.path, b.path, ''))=4) as b
where test.id = b.id

Tdf(79187675) 13:17:20 
declare @TT table
    (
      id int
    , ParentId int
    , path varchar(100)
    )
insert into @TT
        ( id , path )
    values
        ( 1 , 'aaa' ),
        ( 2 , 'aaa/aab' ),
        ( 3 , 'aaa/aac' ),
        ( 4 , 'aaa/aab/aaa' ),
        ( 5 , 'aaa/aac/aa' ) ;
;
with    TT
          as ( select
                    *
                from
                    @TT
                where
                    charindex('/' , path) = 0
                   -- id in ( 2 , 3 )
               union all
               select
                    T1.id , TT.id , T1.path
                from
                    @TT T1
                  , TT
                where
                    len(TT.path) < len(T1.path)
                    and left(T1.path , len(TT.path)) = TT.path
                    and substring(T1.path , len(TT.path) + 2 , len(T1.path) - len(TT.path)) not like '%/%'
             )
    select
            *
        from
            TT

Kenny(27694100) 13:21:09
update test set parentid = b.id
  from test ,(select * from test) b
    where left(a.path,len(b.path)) = b.path and len(a.path) = len(b.path)+4