SQL Server query for tournament matches

Question

I have a table for storing matches (games or whatever you want to call them) for the purpose of being able to view a bracket for a single division.

Here's the table:

CREATE TABLE [dbo].[Match]
(
    [MatchID] [bigint] IDENTITY(1,1) NOT NULL,
    [OrgDivisionID] [bigint] NOT NULL,
    [MatchTimeLength] [bigint] NULL,
    [ParentMatchID1] [bigint] NULL,
    [ParentMatchID2] [bigint] NULL,

    CONSTRAINT [PK_Match] 
        PRIMARY KEY CLUSTERED ([MatchID] ASC)
)

Sample Data:

MatchID OrgDivisionID   MatchTimeLength ParentMatchID1  ParentMatchID2
----------------------------------------------------------------------
 1      1               180             NULL            NULL
 2      1               180             NULL            NULL
 3      1               180             NULL            NULL
 4      1               180             NULL            NULL
 5      1               180             1               2
 6      1               180             3               4
 7      1               180             5               6

(The details of who or what team is involved in a match will be stored in a separate table which is not relevant now.)

The idea is that, a single match can come from zero parent MatchIDs (in that case it is a initial matches/first round) OR 1 or 2 parent MatchIDs.

IF a match has only 1 parent MatchID that would mean that the match was generated with a person who had a "bye" vs a person who previously competed.

IF a match has 2 parent MatchIDs that would mean that the match was generated with both people who previously competed.

What I need help with is a query that will show the full path of all the matches. For example MatchID 1 -> MatchID 5 -> MatchID 7

Any help or suggestions would be great. Thanks

Answer 1

Common Table Expressions (CTE) fit best this task.

;with cte as (
--anckor query
select MatchID,ParentMatchID1,ParentMatchID2, 1 lvl
from #match
where matchid = 1 --or other id
union all -- note: UNION ALL
--recursive query
select m.MatchID,m.ParentMatchID1,m.ParentMatchID2,  lvl+1
from #match m
inner join cte on cte.matchid = m.ParentMatchID1 or cte.matchid = m.ParentMatchID2
)
--Get result from here
select * from cte