Join tables with distinct highest ranked row - sql

Question

I have three tables defined like this:
[tbMember]
memberID | memberName
1 | John
2 | Peter
[tbGroup]
groupID | groupName
1 | Alpha
2 | Beta
3 | Gamma
[tbMemberGroupRelation]
memberID | groupID | memberRank (larger number is higher)
1 | 1 | 0
1 | 2 | 1
2 | 1 | 5
2 | 2 | 3
2 | 3 | 1
And now I want to perform a table-join selection to get result which contains (distinct) member with his highest ranked group in each row, for the given example above, the query result is desired to be:
memberID | memberName | groupName | memberRank
1 | John | Beta | 1
2 | Peter | Alpha | 5
Is there a way to implement it in a single SQL like following style ?
select * from tbMember m
left join tbMemberGroupRelation mg on (m.MemberID = mg.MemberID and ......)
left join tbGroup g on (mg.GroupID = g.GroupID)
Any other solutions are also appreciated if it is impossible to write in a simple query.
========= UPDATED =========
Only ONE highest rank is allowed in table

Answer 1

One solution would be to create an inverted sequence/rank of the memberRank so that the highest rank per member is always equal to 1.
This is how I achieved it using a sub-query:
SELECT
m.memberID,
m.memberName,
g.groupName,
mg.memberRank
FROM
tbMember m
LEFT JOIN
(
SELECT
memberID,
groupID,
groupName,
memberRank,
RANK() OVER(PARTITION BY memberID ORDER BY memberRank DESC) AS invRank
FROM
tbMemberGroupRelation
) mg
ON (mg.memberID = m.memberID)
AND (mg.invRank = 1)
LEFT JOIN
tbGroup g
ON (g.groupID = mg.groupID);

Answer 2

An alternative method:
SELECT
M.memberID,
M.memberName,
G.groupName,
MG.memberRank
FROM
Member M
LEFT OUTER JOIN MemberGroup MG ON MG.memberID = M.memberID
LEFT OUTER JOIN MemberGroup MG2 ON
MG2.memberID = M.memberID AND
MG2.memberRank > MG.memberRank
INNER JOIN [Group] G ON G.groupid = MG.groupid
WHERE
MG2.memberid IS NULL
Might perform better in some situations due to indexing, etc.

Answer 3

create table [tbGroup] (groupid int, groupname varchar(8000))
Insert [tbGroup] Values (1, 'Alpha')
Insert [tbGroup] Values (2, 'Beta')
Insert [tbGroup] Values (3, 'Gamma')
create table [tbMemberGroupRelation] (memberid int, groupid int, memberrank int)
Insert [tbMemberGroupRelation] Values (1,1,0)
Insert [tbMemberGroupRelation] Values (1,2,1)
Insert [tbMemberGroupRelation] Values (2,1,5)
Insert [tbMemberGroupRelation] Values (2,2,3)
Insert [tbMemberGroupRelation] Values (2,3,1)
;With cteMemberGroupRelation As
(
Select *, Row_Number() Over (Partition By MemberID Order By MemberRank Desc) SortOrder
From [tbMemberGroupRelation]
)
Select *
From tbMember M
Join (Select * From cteMemberGroupRelation Where SortOrder = 1) R On R.memberid = M.memberid
Join tbGroup G On G.groupid = R.groupid