提高查询新增数据记录速度的方法

作者：iamlaosong

我们经常需要查询新增的数据记录，比如新开发的客户，这就需要判断这些客户原来是否存在，用的比较多的是用not exists来区分新增客户。当数据库表记录很多时，查询速递需要很长时间，长得难以忍受。

例如，我们查询新增客户量收，语句如下：

select b.city,b.ssxs,a.clct_bureau_org_code,b.zj_mc,a.sender_cust_code,a.sender_dept_name,
       min(a.clct_date),max(a.clct_date),count(*) yjzl,sum(a.actual_total_fee) yjsr
  from tb_evt_mail_clct a, (select * from sncn_zd_jg where jgfl = 'sd') b
 where a.clct_bureau_org_code = b.zj_code
   and a.clct_date between to_date('2013-11-1', 'yyyy-mm-dd') and
       to_date('2013-11-10', 'yyyy-mm-dd')
   and length(a.sender_cust_code) = 14
   and not exists (select 1 from tb_evt_mail_clct t 
         where t.clct_date between to_date('2013-1-1', 'yyyy-mm-dd') and
               to_date('2013-10-31', 'yyyy-mm-dd')
           and t.sender_cust_code = a.sender_cust_code)
 group by b.city,b.ssxs,a.clct_bureau_org_code,b.zj_mc,a.sender_cust_code,a.sender_dept_name
 order by b.city,b.ssxs,a.clct_bureau_org_code,b.zj_mc,a.sender_cust_code,a.sender_dept_name

这个查询需要几个小时才能出来，如果换一种方法，采用下面的语句，只要几十秒就可以了。

select b.city,b.ssxs,a.clct_bureau_org_code,b.zj_mc,a.sender_cust_code,a.sender_dept_name,
       min(a.clct_date),max(a.clct_date),count(*) yjzl,sum(a.actual_total_fee) yjsr
  from tb_evt_mail_clct a, (select * from sncn_zd_jg where jgfl = 'sd') b,
  (select distinct t.sender_cust_code from tb_evt_mail_clct t 
         where t.clct_date between to_date('2013-1-1', 'yyyy-mm-dd') and
               to_date('2013-10-31', 'yyyy-mm-dd')) c
 where a.clct_bureau_org_code = b.zj_code
   and a.clct_date between to_date('2013-11-1', 'yyyy-mm-dd') and
       to_date('2013-11-10', 'yyyy-mm-dd')
   and length(a.sender_cust_code) = 14
   and a.sender_cust_code=c.sender_cust_code(+)
   and c.sender_cust_code is null
 group by b.city,b.ssxs,a.clct_bureau_org_code,b.zj_mc,a.sender_cust_code,a.sender_dept_name
 order by b.city,b.ssxs,a.clct_bureau_org_code,b.zj_mc,a.sender_cust_code,a.sender_dept_name