数据库共708.6万行，数据388MB，索引213MB共600MB。查周数据第一次查询587行用281ms，以后几次为47ms和63ms，查日数据2846行，花费125ms。

没有进行过SQL的优化，谁能改进查询请在下面跟贴。下面是我的代码：

library(RODBC)
#连接数据库
channel <- odbcConnect("postgresql35w", uid="postgres", pwd="admin")

#从股价数据库中读入上证日指数
a<- sqlQuery(channel ,"
SELECT
  stockprice.date,
  stockprice.price
FROM
  public.stockprice
WHERE
  stockprice.code = 'SH000001' AND
  stockprice.date > '1997-10-28'
ORDER BY
  stockprice.date ASC")

#从股价数据库中读入深证日指数
sz<- sqlQuery(channel ,"
SELECT
  stockprice.date,
  stockprice.price
FROM
  public.stockprice
WHERE
  stockprice.code = 'SZ399001' AND
  stockprice.date > '1997-10-28'
ORDER BY
  stockprice.date ASC")

#从股价数据库中读入相关股票周价格
gg<- sqlQuery(channel ,"
select * from
  (select LAST_VALUE(date) OVER (PARTITION  BY to_char(date , 'IYYYIW')) as Wdate,
          LAST_VALUE(price)  OVER (PARTITION  BY to_char(date , 'IYYYIW')) as Wprice
    from (
SELECT
    stockprice.date,
    stockprice.price
FROM
    public.stockprice
WHERE
    stockprice.code = 'SH600030' AND
    stockprice.date > '1997-10-28'
ORDER BY
    stockprice.date ASC) as  ap) as week
group by Wdate , Wprice
order by Wdate")
#断开数据库连接
odbcClose(channel)