Question

我正在尝试提高下面的查询速度，但无法更改必填字段。所以我被困在这里。请帮我摆脱这个陷阱。一点点提示或灵感也很有用!!

select cg.province_id,
   (select count(distinct(c.guidance_user_id))
      from case_guidance c
     where c.guidance_status = '2'
       and c.province_id = cg.province_id) as guidance_cnt,
   (select count(distinct(c.guidance_user_id))
      from case_guidance c
     where c.guidance_status = '2'
       and c.guidance_user_type = 'role.type.teacher'
       and c.province_id = cg.province_id) as guidance_teacher_cnt,
   (select count(distinct(c.guidance_user_id))
      from case_guidance c
     where c.guidance_status = '2'
       and c.guidance_user_type = 'role.type.jyy'
       and c.province_id = cg.province_id) as guidance_jyy_cnt,
   (select count(distinct(c.guidance_user_id))
      from case_guidance c
     where c.guidance_status = '2'
       and c.guidance_user_type = 'role.type.expert'
       and c.province_id = cg.province_id) as guidance_expert_cnt,
   (select count(distinct(c.case_id))
      from case_guidance c
     where c.guidance_status = '2'
       and c.province_id = cg.province_id) as guidance_case_cnt
from case_guidance cg
where cg.province_id is not null
group by cg.province_id
order by guidance_cnt desc

Answer 1

将相关子查询替换为instance1以消除所有连接：

instance2

（我故意将代码行留得更长，以便条件排成一行。这有助于明确列之间的差异，以及它们几乎完全相同的事情。）< / p>

尝试优化PL / SQL查询

1 个答案: