This will work with 2000:
SELECT
A.RetailerID,
b.RetailerIDTheirs
FROM TableA AS A
LEFT JOIN TableB AS B
ON A.RetailerID = B.RetailerID
AND b.RetailerIDTheirs = (SELECT TOP 1 B2.RetailerIDTheirs
FROM TableB B2
WHERE B2.RetailerID = A.RetailerID
ORDER BY B2.RetailerIDTheirs ASC)
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning