SQL2005,新手~查询速度过慢,小弟我应该如何写SQL文

SQL2005,新手求助~~查询速度过慢,我应该怎么写SQL文
数据表如下
A 订单流程序号定义 字段:listID,sequence(序号)
B 订单计划 字段:listID,PL(工作组名称),planNum(计划量),prodate(日期)
C 订单数据 字段:listID,PL(工作组名称),proNum(生产量),sequence(序号),prodate(日期)

查询选定日期的订单信息 (还有未考虑的情况?)
1 有订单计划,有订单生产数据
2 有订单计划,无订单数据
3 无订单计划,有订单数据

查询结果
1 ListID (上面3种情况下出现的ListID)
2 PL B.PL/C.PL (出现第三种情况为C.PL)
3 Everyday_PlanNum 当日计划量 (B.planNum 按listID 和 工作组别 查询 )
4 当日生产量(序号为最大MAX(A.sequence) 的数量和sum(C.proNum) )
5 总的生产量(序号为最大MAX(A.sequence) 的数量和sum(C.proNum) )

求助: C表中数据很多,导致查询速度比较慢,
我知道我写的很烂,求批评,求教育.我应该怎么写啊!!只要出来上面五个查询结果,速度要快--当日出现的ListID,工作组别
select distinct ListID,PL,Everyday_PlanNum  
from  
  (
  select B.ListID,B.PL,B.planNum as Everyday_PlanNum
  from B
  where B.prodate='2011-10-24'

  union all  

  select C.ListID,C.PL,0 as Everyday_PlanNum
  from c
  left join  
  (
  select B.listID,B.PL from B  
  where B.proDate='2011-10-24'
  ) planNum on (planNum.ListID=C.ListID and planNum.PL=C.PL)
  where C.prodate='2011-10-24'
  and planNum.PL is null

  ) P




--当日订单生产量
select C.ListID,C.PL,sum(C.ProNum) as Everyday_ProNum
from C  
inner join  
  (
  select A.ListID,max(A.sequence) as sequence 
  from A group by A.ListID
  ) SelSectionNo on (SelSectionNo.ListID=C.ListID and SelSectionNo.sequence=C.sequence)
where C.ProDate='2011-10-24'  
group by C.ListID,C.LineCode




--总的生产量
select C.ListID,C.PL,sum(C.proNum) as Sum_ProNum
from C
inner join  
  (
  select A.ListID,max(A.sequence) as sequence
  from A group by A.ListID
  ) SelSectionNo on (SelSectionNo.ListID=C.ListID and C.sequence=SelSectionNo.sequence)
inner join  
  (
  select distinct ListID
  from
  (
  select B.ListID from B where B.prodate='2011-10-24'

  union all  

  select C.ListID from C where C.prodate='2011-10-24'
  ) B
  ) F on (C.ListID=C.ListID)
group by C.ListID,C.LineCode 


------解决方案--------------------

SQL code

作组别select distinct ListID,PL,Everyday_PlanNum  from    (  select B.ListID,B.PL,B.planNum as Everyday_PlanNum  from B  where B.prodate='2011-10-24'  union all    select C.ListID,C.PL,0 as Everyday_PlanNum  from c  left join    (  select B.listID,B.PL from B    where B.proDate='2011-10-24'  ) planNum on (planNum.ListID=C.ListID and planNum.PL=C.PL)  where C.prodate='2011-10-24'  and planNum.PL is null
------解决方案--------------------
SQL code
--当日订单生产量select C.ListID,C.PL,sum(C.ProNum) as Everyday_ProNumfrom C   inner join     (  select A.ListID,max(A.sequence) as sequence    from A group by A.ListID  ) SelSectionNo on (SelSectionNo.ListID=C.ListID and SelSectionNo.sequence=C.sequence)where C.ProDate='2011-10-24'   group by C.ListID,C.LineCode---这个真的已经比较简单了