I need to be able to return a list of all children given a parent Id at all levels using SQL.
The table looks something like this:
ID ParentId Name
---------------------------------------
1 null Root
2 1 Child of Root
3 2 Child of Child of Root
Give an Id of '1', how would I return the entire list...? There is no limitation on the depth of the nesting either...
Thanks,
Kieron
To get all children for a given #ParentId stored in that manner you could use a recursive CTE.
declare #ParentId int
--set #ParentId = 1
;WITH T AS
(
select 1 AS ID,null AS ParentId, 'Root' as [Name] union all
select 2,1,'Child of Root' union all
select 3,2,'Child of Child of Root'
),
cte AS
(
SELECT ID, ParentId, Name
FROM T
WHERE ParentId = #ParentId OR (ParentId IS NULL AND #ParentId IS NULL)
UNION ALL
SELECT T.ID, T.ParentId, T.Name
FROM T
JOIN cte c ON c.ID = T.ParentId
)
SELECT ID, ParentId, Name
FROM cte
OPTION (MAXRECURSION 0)
Related
I have a table that has parent and child key relationship in the same table, I need to find Parent rows that don't have any children(for example row 1 have no other children) and the most recent children (for example like row 17 have 3 children i.e. 10,13,14 and we need to fetch most recent children only which is 10 )
You need one part related to be main parent:
SELECT parent.*
FROM MyTable AS parent
WHERE parent_id = 0
Next you need to find most recent direct child:
SELECT parent.*, child.*
FROM MyTable AS parent
LEFT JOIN MyTable AS child
ON child.parent_id = parent.id
WHERE parent_id = 0
AND RANK() OVER (PARTITION BY child.parent_id ORDER BY child.id DESC) = 1
And add no-child ones:
SELECT parent.*, child.*
FROM MyTable AS parent
LEFT JOIN MyTable AS child
ON child.parent_id = parent.id
WHERE parent_id = 0
AND (
RANK() OVER (PARTITION BY child.parent_id ORDER BY child.id DESC) = 1
OR child.id IS NULL)
Something like this should work, but may not be the most efficient way of doing it:
select {desired fields}
from your_table
where not exists
(
select 1 from your_table B
where B.parent_id = your_table.id
)
UNION
select {desired fields}
from your_table
where id in
(
select max(id)
from your_table B
where B.parent_id = your_table.id
)
Hmmm . . . You seem to want one row per parent. Either the most recent child or the parent if there are no children. You can actually do this with window functions:
select t.*
from (select t.*,
row_number() over (partition by coalesce(nullif(parent_id, 0), id
order by parent_id desc, id desc
) as seqnum
from t
) t
where seqnum = 1;
I need to use the same list of values in several IN clauses and I tried doing that with a WITH statement, but can't get it to work correctly.
Here's an example query:
SELECT * FROM parent WHERE
id IN (SELECT first_id FROM child WHERE id=119896 UNION ALL
SELECT second_id FROM child WHERE id=119896 UNION ALL
SELECT third_id FROM child WHERE id=119896) OR
id IN (SELECT was_first_id FROM parent WHERE id IN (SELECT first_id FROM child WHERE id=119896 UNION ALL
SELECT second_id FROM child WHERE id=119896 UNION ALL
SELECT third_id FROM child WHERE id=119896)) OR
id IN (SELECT was_second_id FROM parent WHERE id IN (SELECT first_id FROM child WHERE id=119896 UNION ALL
SELECT second_id FROM child WHERE id=119896 UNION ALL
SELECT third_id FROM child WHERE id=119896)) OR
id IN (SELECT was_third_id FROM parent WHERE id IN (SELECT first_id FROM child WHERE id=119896 UNION ALL
SELECT second_id FROM child WHERE id=119896 UNION ALL
SELECT third_id FROM child WHERE id=119896));
I was hoping to make it so that the 3 queries that are combined in the UNION ALL could be defined in a WITH and then re-used to simplify the query, and it would be nice if it improved performance as well.
Is there a good way to do this?
I would suggest
SELECT *
FROM parent
WHERE (
SELECT id IN (first_id, second_id, third_id)
FROM child
WHERE id = 119896
) OR (
SELECT id IN (was_first_id, was_second_id, was_third_id)
FROM parent
WHERE (
SELECT id IN (first_id, second_id, third_id)
FROM child
WHERE id = 119896
)
);
(I don't know about performance - as per comments, it's really bad)
An alternative, using the CTEs you suggested, would be
WITH child_ids AS (
SELECT UNNEST(ARRAY[first_id, second_id, third_id]) AS id
FROM child
WHERE id = 119896
), all_ids AS (
SELECT UNNEST(ARRAY[was_first_id, was_second_id, was_third_id]) AS id
FROM parent
JOIN child_ids USING (id) -- same as: WHERE id IN (SELECT id FROM child_ids)
UNION
TABLE child_ids
)
SELECT *
FROM parent
JOIN all_ids USING (id) -- same as: WHERE id IN (SELECT id FROM all_ids)
Based on the second solution by #Bergi, this also works as well:
WITH in_child(id) AS (
SELECT first_id FROM child WHERE id=119896 UNION ALL
SELECT second_id FROM child WHERE id=119896 UNION ALL
SELECT third_id FROM child WHERE id=119896
),
in_parent(id) AS (
(SELECT id FROM in_child) UNION ALL
(SELECT was_first_id FROM parent WHERE id IN (SELECT id FROM in_child)) UNION ALL
(SELECT was_second_id FROM parent WHERE id IN (SELECT id FROM in_child)) UNION ALL
(SELECT was_third_id FROM parent WHERE id IN (SELECT id FROM in_child))
)
SELECT * FROM parent WHERE
id IN (SELECT id FROM in_parent);
Given a child id, I need to return a query containing all parents of that child as well as their parents till I get to the root parent.
For example, given this data:
ID / Parent ID
1 / 0
2 / 1
3 / 2
4 / 0
5 / 3
So if I passed in ID 5 I would like to get a query with the results:
ID / Parent ID
1 / 0
2 / 1
3 / 2
This table does not work with a hierarchyid type so I suspect that this will need to be done with a CTE, but have no clue how. If it can be done in an SQL query / proc, any help would be appreciated.
Thanks
This is more or less what you want:
-- CTE to prepare hierarchical result set
;WITH #results AS
(
SELECT id,
parentid
FROM [table]
WHERE id = #childId
UNION ALL
SELECT t.id,
t.parentid
FROM [table] t
INNER JOIN #results r ON r.parentid = t.id
)
SELECT *
FROM #results;
Reference:
CTE: Common Table Expression
Working example:
-- create table with self lookup (parent id)
CREATE TABLE #tmp (id INT, parentid INT);
-- insert some test data
INSERT INTO #tmp (id, parentid)
SELECT 1,0 UNION ALL SELECT 2,1 UNION ALL SELECT 3,2
UNION ALL SELECT 4,0 UNION ALL SELECT 5,3;
-- prepare the child item to look up
DECLARE #childId INT;
SET #childId = 5;
-- build the CTE
WITH #results AS
(
SELECT id,
parentid
FROM #tmp
WHERE id = #childId
UNION ALL
SELECT t.id,
t.parentid
FROM #tmp t
INNER JOIN #results r ON r.parentid = t.id
)
-- output the results
SELECT *
FROM #results
WHERE id != #childId
ORDER BY id;
-- cleanup
DROP TABLE #tmp;
Output:
1 | 0
2 | 1
3 | 2
I would like to know how to write a postgres subquery so that the following table example will output what I need.
id parent_id postdate
1 -1 2015-03-10
2 1 2015-03-11 (child level 1)
3 1 2015-03-12 (child level 1)
4 3 2015-03-13 (child level 2)
5 -1 2015-03-14
6 -1 2015-03-15
7 6 2015-03-16 (child level 1)
If I want to sort all the root ids by child level 1 with a count of children(s) from the parent, the output would be something like this
id count date
6 2 2015-03-15
1 4 2015-03-10
5 1 2015-03-14
The output is sorted by postdate based on the root's child. The 'date' being outputted is the date of the root's postdate. Even though id#5 has a more recent postdate, the rootid#6's child (id#7) has the most recent postdate because it is being sorted by child's postdate. id#5 doesnt have any children so it just gets placed at the end, sorted by date. The 'count' is the number children(child level 1), grandchildren(child level 2) and itself (root). For instance, id #2,#3,#4 all belong to id#1 so for id#1, the count would be 4.
My current subquery thus far:
SELECT p1.id,count(p1.id),p1.postdate
FROM mytable p1
LEFT JOIN mytable c1 ON c1.parent_id = p1.id AND p1.parent_id = -1
LEFT JOIN mytable c2 ON c2.parent_id = c1.id AND p1.parent_id = -1
GROUP BY p1.id,c1.postdate,p1.postdate
ORDER by c1.postdate DESC,p1.postdate DESC
create table mytable ( id serial primary key, parent_id int references mytable, postdate date );
create index mytable_parent_id_idx on mytable (parent_id);
insert into mytable (id, parent_id, postdate) values (1, null, '2015-03-10');
insert into mytable (id, parent_id, postdate) values (2, 1, '2015-03-11');
insert into mytable (id, parent_id, postdate) values (3, 1, '2015-03-12');
insert into mytable (id, parent_id, postdate) values (4, 3, '2015-03-13');
insert into mytable (id, parent_id, postdate) values (5, null, '2015-03-14');
insert into mytable (id, parent_id, postdate) values (6, null, '2015-03-15');
insert into mytable (id, parent_id, postdate) values (7, 6, '2015-03-16');
with recursive recu as (
select id as parent, id as root, null::date as child_postdate
from mytable
where parent_id is null
union all
select r.parent, mytable.id, mytable.postdate
from recu r
join mytable
on parent_id = r.root
)
select m.id, c.cnt, m.postdate, c.max_child_date
from mytable m
join ( select parent, count(*) as cnt, max(child_postdate) as max_child_date
from recu
group by parent
) c on c.parent = m.id
order by c.max_child_date desc nulls last, m.postdate desc;
You'll need a recursive query to count the elements in the subtrees:
WITH RECURSIVE opa AS (
SELECT id AS par
, id AS moi
FROM the_tree
WHERE parent_id IS NULL
UNION ALL
SELECT o.par AS par
, t.id AS moi
FROM opa o
JOIN the_tree t ON t.parent_id = o.moi
)
SELECT t.id
, c.cnt
, t.postdate
FROM the_tree t
JOIN ( SELECT par, COUNT(*) AS cnt
FROM opa o
GROUP BY par
) c ON c.par = t.id
ORDER BY t.id
;
UPDATE (it appears the OP also wants the maxdate per tree)
-- The same, but also select the postdate
-- --------------------------------------
WITH RECURSIVE opa AS (
SELECT id AS par
, id AS moi
, postdate AS postdate
FROM the_tree
WHERE parent_id IS NULL
UNION ALL
SELECT o.par AS par
, t.id AS moi
-- , GREATEST(o.postdate,t.postdate) AS postdate
, t.postdate AS postdate
FROM opa o
JOIN the_tree t ON t.parent_id = o.moi
)
SELECT t.id
, c.cnt
, t.postdate
, c.maxdate
FROM the_tree t
JOIN ( SELECT par, COUNT(*) AS cnt
, MAX(o.postdate) AS maxdate -- and obtain the max()
FROM opa o
GROUP BY par
) c ON c.par = t.id
ORDER BY c.maxdate, t.id
;
After looking at everyone's code, I created the subquery I needed. I can use PHP to vary the 'case when' code depending on the user's sort selection. For instance, the code below will sort the root nodes based on child level 1's postdate.
with recursive cte as (
select id as parent, id as root, null::timestamp as child_postdate,0 as depth
from mytable
where parent_id = -1
union all
select r.parent, mytable.id, mytable.postdate,depth+1
from cte r
join mytable
on parent_id = r.root
)
select m.id, c.cnt, m.postdate
from ssf.dtb_021 m
join ( select parent, count(*) as cnt, max(child_postdate) as max_child_date,depth
from cte
group by parent,depth
) c on c.parent = m.id
order by
case
when depth=2 then 1
when depth=1 then 2
else 0
end DESC,
c.max_child_date desc nulls last, m.postdate desc;
select
p.id,
(1+c.n) as parent_post_plus_number_of_subposts,
p.postdate
from
table as p
inner join
(
select
parent_id, count(*) as n, max(postdate) as _postdate
from table
group by parent_id
) as c
on p.id = c.parent_id
where p.parent_id = -1
order by c._postdate desc
I have this self-referencing table where-in I should get the upline and downline and hierarchy levels without the Parent ID provided.
Any ideas?
Have you tried using recursive CTE?
for example:
assume you have table tbl(EmpId, Name, MngrId) which has self-referencing relationship
create table tbl
(
EmpId int not null,
Name nvarchar(100),
MngrId int null)
insert into tbl(EmpId, Name, MngrId)
values (1,'Adel',Null),
(2,'Ali',1),
(3,'Shaban',1),
(4,'Mark',3),
(5,'John',3),
(6,'Tony',Null),
(7,'Peter',6)
You can create some view like that:
create view Employees
Begin
with cte
as
(
Select EmpId,Name, Null as MngrId, cast(null as nvarchar(100)) as MngrName, 1 as EmpLevel
from tbl
where MngrId is Null
Union All
Select t.EmpId, t.Name, c.EmpId as MngrId, c.Name as MngrName, c.EmpLevel + 1 as EmpLevel
from tbl t
inner join cte c
on t.MngrId = c.EmpId
)
Select *
from cte
order by EmpLevel, EmpId
End
You can now use EmpLevel to jump between different levels and MngrName to get information about parent node