Oracle sql语句优化

1：查询的数据量比较大的时候采用建立索引的方式

之前写了一个sql 查询速度在24秒

SELECT distinct sp.mr_rte_cd,
                cardinfo.acct_id,
                sp.sp_id,
                cardinfo.mtr_id,
                (select pn.entity_name
                   from ci_per_name pn,
                        ci_acct_per ap,
                        ci_acct     acct,
                        cm_sp_acct  v
                  where ap.per_id = pn.per_id
                    and ap.acct_id = acct.acct_id
                    and v.SP_ID = sp.sp_id
                    and v.ACCT_ID = acct.acct_id
                    and pn.prim_name_sw = 'Y') entity_name,
                (select v.address1
                   from cm_sp_acct v
                  where v.SP_ID = sp.sp_id) address,
                (select Max(info.read_dttm)
                   from cm_bus_cardinfo info
                  where info.sp_id = sp.sp_id) lastReadDate, 
                (select a.cm_mr_base
                   from cm_bus_cardinfo a
                  where a.sp_id = sp.sp_id
                    and a.read_dttm =
                        (select Max(info.read_dttm)
                           from cm_bus_cardinfo info
                          where info.sp_id = sp.sp_id)) lastMrRead,
                (select a.cm_card_remain
                   from cm_bus_cardinfo a
                  where sp.sp_id = a.sp_id
                    and a.read_dttm =
                        (select Max(info.read_dttm)
                           from cm_bus_cardinfo info
                          where info.sp_id = sp.sp_id)) lastCardRemain,
                (select a.cm_mtr_remain
                   from cm_bus_cardinfo a
                  where a.sp_id = sp.sp_id
                    and a.read_dttm =
                        (select Max(info.read_dttm)
                           from cm_bus_cardinfo info
                          where info.sp_id = sp.sp_id)) lastMtrRemain,
                trunc(SYSDATE) mrDTTM, -1 regReading,-1 cardRemain, -1 mtrRemain,
                (select decode(sum(bus.cm_tran_qty),
                               0,
                               sum((bus.cm_price * bus.cm_tran_amt))) 
                   from cm_cpu_gas_tran_bus bus
                  where bus.sp_id = sp.sp_id
                    and bus.cm_tran_status = 'Y'
                    and bus.cm_tran_type in ('01', '04')) qtyCount,
               (select a.full_scale
                   from ci_reg a
                  where a.mtr_id = cardinfo.mtr_id) fullScale,
                (select mtr.mtr_type_cd
                   from ci_mtr mtr
                  where mtr.mtr_id = cardinfo.mtr_id) mtrTypeCd               
                
  FROM ci_sp sp, cm_bus_cardinfo cardinfo
 WHERE 1 = 1
   AND cardinfo.sp_id = sp.sp_id 
   AND sp.mr_rte_cd = 'GF0028'

在from和where部分的表字段上加了索引，查询就是瞬间的事情

建立索引：

 　　Create Index read_dttm On cm_bus_cardinfo(read_dttm)

　　read_dttm   ----索引名称

　　cm_bus_cardinfo   ---表名

　　read_dttm   ---表字段名称

2：查询的sql语句尽量减少使用null和in做为筛选条件，因为索引会失效