Delete the same reference multiple columns rows safely? - sql

Question

I need to find all the parent-children relationships, which are all linked to my primary column ID
How I can delete the same reference columns in the table? Let say for example,if I want to delete "Google", I have to delete "HP" and Intel first also the child of HP as well.
I have tried the below thus far, but that works with only one column.
WITH tb (id,Name, Level, Path, Parent)
AS
(
SELECT
id,Name, 1 AS Level,
CAST('/'+Name as nvarchar(max)) as Path,
CAST(NULL as nvarchar(max)) as Parent
FROM krishtest
WHERE parent1 IS NULL
UNION All
SELECT
e.id,e.Name, x.Level + 1 AS Level, x.Path + '/' + e.Name as Path,
REVERSE(SUBSTRING( REVERSE(x.[Path]) ,0 , CHARINDEX( '/', REVERSE(x.[Path])) )) as [Parent]
FROM krishtest e
JOIN tb x ON x.id = e.parent1
)
SELECT Name, Level, Path, Parent FROM tb

Answer 1

is this use full?
declare #tmp table (id int, Name varchar(10),Parent1 int,Parent2 int,Parent3 int,Parent4 int,Parent5 int)
insert into #tmp
SELECT 1,'Microsoft',NULL,NULL,NULL,NULL,NULL
union
SELECT 2,'Google',1,NULL,NULL,NULL,NULL
union
SELECT 3,'HP',NULL,2,NULL,NULL,NULL
union
SELECT 4,'Amazone',NULL,NULL,3,NULL,NULL
union
SELECT 5,'FB',NULL,NULL,NULL,4,NULL
union
SELECT 6,'Yahoo',NULL,NULL,NULL,4,NULL
union
SELECT 7,'Intel',NULL,NULL,2,NULL,NULL
union
SELECT 8,'Apple',7,5,NULL,NULL,NULL
select * from #tmp
;with name_tree as (
select *
from #tmp
where id = 2
union all
select c.*
from #tmp c
join name_tree p on (p.id = c.parent1 or p.id = c.parent2 or p.id = c.parent3 or p.id = c.parent4 or p.id = c.parent5)
)
delete from t
from #tmp t
JOIN name_tree c on t.id=c.id
select * from #tmp

Answer 2

I haven't provided an actual solution to your issue here. But I would recommend investigating recursive Common Table Expressions. That should allow you to find all the parent records, then you can run a delete on them.
https://technet.microsoft.com/en-us/library/ms186243(v=sql.105).aspx

Answer 3

You can simply modify the recursive CTE's where clause like in below query to get all rows that need to be deleted.
See live demo
create table krishtest (id int, name varchar(100), parent1 int, parent2 int)
insert into krishtest values
(1,'Microsoft', NULL, NULL),
(2,'Google',1,NULL),
(3,'HP',NULL,2),
(4,'amazon',3,NULL),
(5,'FB',NULL,4),
(6,'yahoo',3,NULL),
(7,'cisco',6,NULL)
;
WITH tb (id,Name, Level, Path, Parent)
AS
(
SELECT
id,Name, 1 AS Level,
CAST('/'+Name as nvarchar(max)) as Path,
CAST(NULL as nvarchar(max)) as Parent
FROM krishtest
WHERE -- COALESCE(parent1,parent2) IS NULL
name ='HP'
UNION All
SELECT
e.id,e.Name, x.Level + 1 AS Level, x.Path + '/' + e.Name as Path,
REVERSE(SUBSTRING( REVERSE(x.[Path]) ,0 , CHARINDEX( '/', REVERSE(x.[Path])) )) as [Parent]
FROM krishtest e
JOIN tb x ON x.id = COALESCE(e.parent1,e.parent2)
)
--delete FROM krishtest where id in( select id from tb)
--select * from krishtest
SELECT Name, Level, Path, Parent FROM tb