加入三个表，获取每个代理的销售总额

使用 UNION ALL 返回所有代理（主要代理和额外代理）及其相应的销售：

SELECT SUM(t.volume) as SalesVolume, t.AgentName 
FROM (
  SELECT AgentID, AgentNames AS AgentName, 
    SaleValue / CASE WHEN COALESCE(ExtraAgentID, 0) <> 0 THEN 2 ELSE 1 END volume
  FROM [dbo].[PrimeClosureInformation]
  UNION ALL
  SELECT ExtraAgentID, ExtraAgentName, SaleValue / 2
  FROM [dbo].[PrimeClosureInformation]
  WHERE COALESCE(ExtraAgentID, 0) <> 0
) AS t INNER JOIN VW_User AS u
ON u.UserIdLG = t.AgentId 
WHERE u.Status = N'active'
GROUP BY t.AgentName