Sql-server – Optimize query collecting all related items

sql server

The following table is my menu master table that has an unlimited menu depth. Every menu can have a submenu and a sub-submenu and so on.

The problem I am facing is getting all items that have the same top-level parent.

One solution is to loop while parent is not null and second solution is to create a view with a parent id and all sub menu ids with comma separated column.

Then one select command will give the parent id. My table is as follows:

CategoryID  | ParentID    
1           | null        
2           | null        
3           | 1           
4           | 1           
5           | 2           
6           | 2           
7           | 3

Output should be

CategoryID  | AllRelatedCategory
1           | 1,3,4,7
2           | 2,5,6

My current code is as follows. Problem is that it's working only with 3 levels of the hierarchy.

;with cte as
(
select a.CategoryID col1, convert(varchar, a.CategoryID) col2, a.ParentID
from [dbo].[TB_CATEGORY_MASTER] a where a.ParentID is null

union
select a.CategoryID col1, (convert(varchar, isnull(b.CategoryID,''))) col2, a.ParentID
from [dbo].[TB_CATEGORY_MASTER] a 
left join [dbo].[TB_CATEGORY_MASTER] b on a.CategoryID=b.ParentID

union
select a.CategoryID col1, (convert(varchar, isnull(c.CategoryID,''))) col2, a.ParentID
from [dbo].[TB_CATEGORY_MASTER] a 
left join [dbo].[TB_CATEGORY_MASTER] b on a.CategoryID=b.ParentID
left join [dbo].[TB_CATEGORY_MASTER] c on b.CategoryID=c.ParentID
)

select distinct c.col1, 
  STUFF(
         (SELECT distinct ', ' + c1.col2
          FROM cte c1
          where c.col1 = c1.col1
          FOR XML PATH ('')), 1, 1, '') col2
from cte c
where c.ParentID is null

Best Answer

with    cte
        as
        (
            select      CategoryID  as root_CategoryID
                       ,1           as lvl
                       ,CategoryID


            from        TB_CATEGORY_MASTER

            where       ParentID is null


            union all


            select      c.root_CategoryID
                       ,c.lvl + 1
                       ,t.CategoryID

            from                    TB_CATEGORY_MASTER  as t

                        join        cte                 as c

                        on          c.CategoryID = t.ParentID
            )

select     t.CategoryID

          ,(select      case when lvl = 1 then '' else ',' end 
                      + cast (c.CategoryID as varchar(10))

            from        cte as c

            where       c.root_CategoryID = t.CategoryID

            order by    lvl

            for xml path('')
            )                   as AllRelatedCategory

from        TB_CATEGORY_MASTER  as t

where       ParentID is null

+------------+--------------------+
| CategoryID | AllRelatedCategory |
+------------+--------------------+
|          1 | 1,3,4,7            |
|          2 | 2,5,6              |
+------------+--------------------+

Related Solutions

Sql-server – SQL Select taking too much time to execute

I think in a million records query, you have to avoid things like OUTER JOINS. I suggest you use UNION ALL Instead of LEFT JOIN. As long as I think CROSS APPLY is more efficient than sub-query in the select clause I will modify the query written by Conard Frix, which I think is correct.

now: when I started to modify your query I noticed that you have a WHERE clause saying: JoinedTable.WhereColumn IN (1, 3). in this case, if the field is null the condition will become false. then why are you using LEFT JOIN while you are filtering null valued rows? just replace LEFT JOIN With INNER JOIN, I guarantee that it will become faster.

about INDEX:

please note that when you have an index on a table, say

table1(a int, b nvarchar)

and your index is :

nonclustered index ix1 on table1(a)

and you want to do something like this:

select a,b from table1
where a < 10

in your index you have not included the column b so what happens?

if sql-server uses your index, it will have to search in the index, called "Index Seek" and then refer to main table to get column b, called "Look Up". This procedure might take much longer than scanning the table itself: "Table Scan".

but based on the statistics that sql-server has, in such situations, it might not use your index at all.

so first of all check the Execution Plan to see if the index is used at all.

if yes or no both, alter your index to include all columns that you are selecting. say like:

nonclustered index ix1 on table1(a) include(b)

in this case Look Up will not be needed, and your query will execute so much faster.

Sql-server – Item Index for all items in nested XML query

I found the answer - I needed to create a CTE that uses a union of all my child and parent records and creates a ROW_NUMBER(), then JOIN to that CTE to get the ROW_NUMBER() value which will be unique across all records.

Solution fiddle here.

Full solution to paste into SSMS:

BEGIN TRY
    DROP TABLE #Child
    DROP TABLE #Parent
END TRY
BEGIN CATCH
END CATCH

CREATE TABLE #Parent 
    (RecId int PRIMARY KEY NOT NULL, 
     PersonName varchar(100), Age int)
CREATE TABLE #Child 
    (ChildID int identity PRIMARY KEY NOT NULL,
     ParentRecId int FOREIGN KEY REFERENCES #Parent(RecId), 
     SalesAmt money)

INSERT INTO #Parent
  (RecID, PersonName, Age)
VALUES
  (1, 'Aaron Bertrand', 99),
  (2, 'Paul White', 20),
  (3, 'JNK', 33)

INSERT INTO #Child
  (ParentRecID, SalesAmt)
VALUES
  (1, 10.00),
  (1, 20.00),
  (2, 15.15),
  (2, 100.00),
  (3, 0.00)

;WITH IDs AS
(
    SELECT
       RN = (ROW_NUMBER() OVER (ORDER BY  RecId,CASE WHEN ChildId IS NULL THEN 0 ELSE 1 END) -1),
       RecId,
       ChildId
    FROM
       (
       SELECT
          RecId, ChildId = NULL
       FROM
          #Parent
       UNION ALL
       SELECT
          RecId, ChildId
       FROM 
          #Parent P
       INNER JOIN
          #Child C
              ON C.ParentRecId = P.RecId) x
)

SELECT
  P.RecId as 'RID',
  P.PersonName as 'PNAM',
  P.Age,
  I.RN as 'Index',
  (
    SELECT 
      C.SalesAmt as 'SAMT',
      I.RN as 'Index'
    FROM
      #Child C
    INNER JOIN
       IDs I
          ON I.ChildId = C.ChildID
    WHERE
      C.ParentRecId = P.RecId
    FOR XML PATH ('ChildRec'), ROOT ('ChildRecs'), TYPE
  )
FROM
  #Parent P
INNER JOIN
    IDs I
       ON I.RecId = P.RecId
       AND I.ChildId IS NULL
FOR XML PATH ('Parent'), ROOT ('Parents'), TYPE

Best Answer

Related Solutions

Sql-server – SQL Select taking too much time to execute

Sql-server – Item Index for all items in nested XML query

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