SELECt UserID, CASE WHEN EXISTS ( SELECT 1 FROM dbo.Users WHERe UserPeers LIKE '%' + u.UserID + '%') THEN 'I am in Column1' ELSE UserID ENDFROM dbo.Users AS u;

SELECt UserID, CASE WHEN EXISTS ( SELECT 1 FROM dbo.Users WHERe UserPeers LIKE '%' + u.UserID + '%') THEN 'I am in Column1' ELSE UserID ENDFROM dbo.Users AS u;