sql优化-总结

1、尽量缩小数据范围。

2、能一个sql解决的，坚决不用两条sql。利用case when或decode。

select month_id,
       corppkno,
       sum(exportSum_new) exportSum_new,
       sum(exportSum_newLy) exportSum_newLy,
       sum(exportSum_Support) exportSum_Support,
       sum(exportSum_SupportLy) exportSum_SupportLy
  from ( /*当年累计出口*/
        select a.month_id,
                c.corppkno,
                decode(a.isnewinsurant, null, 0, b.exportdollar) exportSum_new,/*此处为了用一条sql实现*/
                0 exportSum_newLy,
                b.exportdollar exportSum_Support,
                0 exportSum_SupportLy
          from (select trunc(t1.month_id / 100) yearid,
                        t1.month_id,
                        t3.cocode,
                        max(t.newinsurantpkno_sm) isnewinsurant /*当月新增的客户*/
                   from stdw.F_Sum_SupportInsurant_SM     t,
                        stdw.lu_month_cumulate            t1,
                        stdw.d_t_customer                 t2,
                        stdw.d_t_Customsenterprisemapping t3
                  where t.monthid = t1.month_cumul_id
                    and t.supportinsuantpkno_sm = t2.pkno
                    and t2.crmno = t3.customno
                    and t3.state = '1'
                    and t1.month_id <= to_char(sysdate - 1, 'YYYYMM')
                  group by t1.month_id, t3.cocode) A,
                stdw.f_custom_company_composite B,
                stdw.d_custom_branch_province C,
                stdw.lu_month_cumulate D /*此sql先用子查询A限定范围，再通过A去关联B。因为B的范围大，如果对B进行汇总后再和A关联，效率较低*/
         where b.monthid = d.month_cumul_id
           and b.corpid = c.corpid
           and a.yearid = b.yearid /*跨区访问*/
           and a.month_id = d.month_id
           and a.cocode = b.cocode
        union all
        /*上年总出口额*/
        select a.month_id,
               b.corppkno,
               0 exportSum_new,
               decode(a.isnewinsurant, null, 0, b.exportdollar) exportSum_newLy,
               0 exportSum_Support,
               b.exportdollar exportSum_SupportLy
          from (select trunc(t1.month_id / 100) - 1 yearid_ly,
                       t1.month_id,
                       t3.cocode,
                       max(t.newinsurantpkno_sm) isnewinsurant /*当月新增的客户*/
                  from stdw.F_Sum_SupportInsurant_SM     t,
                       stdw.lu_month_cumulate            t1,
                       stdw.d_t_customer                 t2,
                       stdw.d_t_Customsenterprisemapping t3
                 where t.monthid = t1.month_cumul_id
                   and t.supportinsuantpkno_sm = t2.pkno
                   and t2.crmno = t3.customno
                   and t3.state = '1'
                   and t1.month_id <= to_char(sysdate - 1, 'YYYYMM')
                 group by t1.month_id, t3.cocode) A,
               (select t1.outputyear  yearid,
                       t1.cocode,
                       t4.corppkno,
                       t1.totaldollar exportdollar
                  from stdw.f_custom_company_total   t1,
                       stdw.d_custom_company         t2,
                       stdw.d_custom_province_zone   t3,
                       stdw.d_custom_branch_province t4
                 where t1.cocode = t2.cocode
                   and t2.zonecode = t3.zone
                   and t3.province_no = t4.proviceid) B
         where a.yearid_ly = B.yearid
           and a.cocode = B.cocode)
 group by month_id, corppkno