SQL优化经典----利用分析函数优化自连接

SQL优化经典----利用分析函数优化自连接

----http://blog.sina.com.cn/s/blog_61cd89f60102efak.html

这几天看到一个不错的SQL优化案例，读完感觉很受启发，在此记录一下优化思路了具体分析过程，对于SQL优化我们的目标是减少逻辑读、减少递归调用，我们来看一下

select distinct decode(length(a.category_id),

5,

decode(a.origin_type, 801, 888888, 999999),

a.category_id) category_id,

a.notice_code,

a.treat_status,

lr.real_name as receiver_name,

f.send_code,

f.policy_code,

g.real_name agent_name,

f.organ_id,

f.dept_id,

a.policy_id,

a.change_id,

a.case_id,

a.group_policy_id,

a.fee_id,

a.auth_id,

a.pay_id,

cancel_appoint.appoint_time cancel_appoint_time,

a.insert_time,

a.send_time,

a.end_time,

f.agency_code,

a.REPLY_TIME,

a.REPLY_EMP_ID,

a.FIRST_DUTY,

a.NEED_SEND_PRINT,

11 source

from t_policy_problem a,

t_policy f,

t_agent g,

t_letter_receiver lr,

t_problem_category pc,

t_policy_cancel_appoint cancel_appoint

where f.agent_id = g.agent_id(+)

and a.policy_id = f.policy_id(+)

and lr.main_receiver = 'Y'

and a.category_id = pc.category_id

and a.item_id = lr.item_id

and a.policy_id = cancel_appoint.policy_id(+)

And a.Item_Id = (Select Max(item_id)

From t_Policy_Problem

Where notice_code = a.notice_code)

and a.policy_id is not null

and a.notice_code is not null

and a.change_id is null

and a.case_id is null

and a.group_policy_id is null

and a.origin_type not in (801, 802)

and a.pay_id is null

and a.category_id not in

(130103, 130104, 130102, 140102, 140101)

and f.policy_type = 1

and (a.fee_id is null or

(a.fee_id is not null and a.origin_type = 701))

and f.organ_id in

(select distinct organ_id

from T_COMPANY_ORGAN

start with organ_id = '107'

connect by parent_id = prior organ_id)

and pc.NEED_PRITN = 'Y'

优化后：

WITH t_Policy_Problem_w AS

(SELECT tp.*, max(item_id) OVER(PARTITION BY notice_code) max_item_id

FROM t_Policy_Problem tp)

select distinct decode(length(a.category_id),

5,

decode(a.origin_type, 801, 888888, 999999),

a.category_id) category_id,

a.notice_code,

a.treat_status,

lr.real_name as receiver_name,

f.send_code,

f.policy_code,

g.real_name agent_name,

f.organ_id,

f.dept_id,

a.policy_id,

a.change_id,

a.case_id,

a.group_policy_id,

a.fee_id,

a.auth_id,

a.pay_id,

cancel_appoint.appoint_time cancel_appoint_time,

a.insert_time,

a.send_time,

a.end_time,

f.agency_code,

a.REPLY_TIME,

a.REPLY_EMP_ID,

a.FIRST_DUTY,

a.NEED_SEND_PRINT,

11 source

from t_Policy_Problem_w a,

t_policy f,

t_agent g,

t_letter_receiver lr,

t_problem_category pc,

t_policy_cancel_appoint cancel_appoint

where a.item_id = a.max_item_id

and f.agent_id = g.agent_id(+)

and a.policy_id = f.policy_id(+)

and lr.main_receiver = 'Y'

and a.category_id = pc.category_id

and a.item_id = lr.item_id

and a.policy_id = cancel_appoint.policy_id(+)

and a.policy_id is not null

and a.notice_code is not null

and a.change_id is null

and a.case_id is null

and a.group_policy_id is null

and a.origin_type not in (801, 802)

and a.pay_id is null

and a.category_id not in (130103, 130104, 130102, 140102, 140101)

and f.policy_type = 1

and (a.fee_id is null or (a.fee_id is not null and a.origin_type = 701))

and f.organ_id in (select distinct organ_id

from T_COMPANY_ORGAN

start with organ_id = '107'

connect by parent_id = prior organ_id)

and pc.NEED_PRITN = 'Y'

利用分析函数max() over(partition by )优化自连接，具体分析详见：

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