Question

我有一个请求，请告诉我如何优化它？

    select distinct
    trunc(dw.mdf_date) as mdf_date
    ,dw.dss_id
    ,dw.raid
    ,dw.host_type
    ,dw.volume_name
    ,dw.volume_size
    ,dw.prv
    ,listagg(dw.hba_wwn,',' on overflow truncate '...' without count) within group (order by dw.hba_wwn) as wwn
  from
    dss_wwn dw
  where
    dw.volume_name not in ('ADMIN')
    and dw.volume_name not like '.%'
    and dw.hba_wwn is not null
    and not exists (select 1 from wwn shw where shw.wwn = dw.hba_wwn and shw.dic_type_eqp_id = 4 and rownum = 1)
    and not exists (select 1 from dss_vmhdd shw where shw.wwid = dw.disk_wwn and rownum = 1)
  group by
    trunc(dw.mdf_date)
    ,dw.dss_id
    ,dw.raid
    ,dw.host_type
    ,dw.volume_name
    ,dw.volume_size
    ,dw.prv

此请求持续23秒。如果您注释掉这一行，那将可以快速运行0.2秒

and not exists (select 1 from wwn shw where shw.wwn = dw.hba_wwn and shw.dic_type_eqp_id = 4 and rownum = 1)

select count(*) from DSS_WWN --100000
select count(*) from WWN t --13000

UPD @Gro感谢您的回答，确实是在我删除rownum = 1请求后，它在0.4秒内完成了

优化SQL，不存在/不存在？

0 个答案: