我想優化下面的查詢。我沒有關於優化技術的專業知識。 請建議我一些東西，可以幫我優化下面的查詢：Oracle查詢優化（帶連接和子查詢）
SELECT
ad.towncity,
ad.state,
FROM promptdescription pd,
osquestion osq,
WHERE acc.status = 1
AND acc.customer_id = con.customer_id
ap.os_id
AND NOT EXISTS (SELECT 1
FROM osquestion osq2,
orderedproduct op3
WHERE osq2.ext_quest_id = pd.id
AND osq2.question_id > osq.question_id
首先，你的查詢等效於：
SELECT ACC.id
, OP.rootprODUCT_ID
, ACC.externALBILLID
, CON.firstnAME
, CON.lastnaME
, AD.line1
, NVL (AD.line2 , '') AS LINE2
, AD.towncity
, AD.state
, AD.postalzipcode
, PROD.billingcode
, PD.name as Prompt_Name
, OSQ.current_value
FROM promptdescription PD
JOIN osquestion OSQ ON OSQ.ext_quest_id = PD.id
JOIN osquestiongroup OSQGRP ON OSQGRP.qg_id = OSQ.qg_id
JOIN osparamdatacapability OSPARAMCAP ON OSPARAMCAP.cap_id = OSQGRP.cap_id
JOIN orderedservice OS ON OS.id = OSPARAMCAP.os_id
JOIN servicedescription SD ON SD.id = OS.svcdesc_id
JOIN orderedproduct OP ON OP.ordservice_id = OS.id
JOIN productdescription PROD ON PROD.id = OP.proddesc_id_root
JOIN customerorder CO ON CO.id = OP.custorder_id
JOIN account ACC ON ACC.id = OP.account_id
JOIN contact C ON C.customer_id = ACC.customer_id
JOIN address ADDR ON ADDR.id = C.address_id
JOIN contact CON ON CON.customer_id = ACC.customer_id
JOIN address AD ON AD.id = CON.address_id
WHERE PD.name IN ('County Code' , 'Service Occurrence' , 'VoIP Port' , 'VoIP MTA MAC address' , 'Primary TN' , 'HSDS CM MAC address' , 'VoIP FQDN' , 'Caller Id')
AND OSQ.current_value IS NOT NULL
AND SD.name in ('Voice over IP')
AND OP.resultingaction <> 2
AND OP.status = 10
AND ACC.status = 1
AND EXISTS (SELECT 1
FROM ORDEREDPRODUCT OP1
WHERE OP1.PRODUCT_ID = OP.PRODUCT_ID
AND OP1.STATUS = 10
HAVING MAX (OP1.ID) = OP.ID)
AND CO.ID IN (select ID
FROM CUSTOMERORDER CO1
where CO1.CUSTOMER_ID = ACC.CUSTOMER_ID
AND CO1.STATUS = 10)
AND NOT EXISTS (SELECT 1
FROM OSQUESTION OSQ2
, ORDEREDSERVICE OS1
, OSPARAMDATACAPABILITY OSPARAMCAP1
, OSQUESTIONGROUP OSQGRP1
, ORDEREDPRODUCT OP3
where OSQ2.EXT_QUEST_ID = PD.ID
AND OSQ2.QUESTION_ID > OSQ.QUESTION_ID
AND OSQ2.PROVISIONED_VALUE = OSQ.CURRENT_VALUE
AND OSQ2.CURRENT_VALUE != OSQ.CURRENT_VALUE
AND PD.NAME IN ('Primary TN'
, 'VoIP MTA MAC address'
, 'HSDS CM MAC address')
AND OSQGRP1.QG_ID = OSQ2.QG_ID
AND OSPARAMCAP1.CAP_ID = OSQGRP1.CAP_ID
AND OS1.ID = OSPARAMCAP1.OS_ID
AND OP.ROOTPRODUCT_ID = OP3.ROOTPRODUCT_ID
AND OP3.ORDSERVICE_ID = OS1.ID
AND OP3.STATUS = 10)
ORDER BY ACC.EXTERNALBILLID
, OP.ROOTPRODUCT_ID
, CO.ID
備註：
我可以重寫第一部分爲：
SELECT ACC.id
, OP.rootprODUCT_ID
, ACC.externALBILLID
, CON.firstnAME
, CON.lastnaME
, AD.line1
, NVL (AD.line2 , '') AS LINE2
, AD.towncity
, AD.state
, AD.postalzipcode
, PROD.billingcode
, PD.name as Prompt_Name
, OSQ.current_value
FROM promptdescription PD
JOIN osquestion OSQ ON OSQ.ext_quest_id = PD.id
JOIN osquestiongroup OSQGRP ON OSQGRP.qg_id = OSQ.qg_id
JOIN osparamdatacapability OSPARAMCAP ON OSPARAMCAP.cap_id = OSQGRP.cap_id
JOIN orderedservice OS ON OS.id = OSPARAMCAP.os_id
JOIN servicedescription SD ON SD.id = OS.svcdesc_id
JOIN orderedproduct OP ON OP.ordservice_id = OS.id
JOIN productdescription PROD ON PROD.id = OP.proddesc_id_root
JOIN account ACC ON ACC.id = OP.account_id
JOIN contact C ON C.customer_id = ACC.customer_id
JOIN address ADDR ON ADDR.id = C.address_id
JOIN contact CON ON CON.customer_id = ACC.customer_id
JOIN address AD ON AD.id = CON.address_id
JOIN customerorder CO ON CO.id = OP.custorder_id
AND CO.customer_id = ACC.customer_id
LEFT JOIN orderedproduct ismaxopid ON ismaxopid.product_id = op.product_id
AND ismaxopid.status = 10
AND ismaxopid.id > op.id
WHERE PD.name IN ('County Code' , 'Service Occurrence' , 'VoIP Port' , 'VoIP MTA MAC address' , 'Primary TN' , 'HSDS CM MAC address' , 'VoIP FQDN' , 'Caller Id')
AND OSQ.current_value IS NOT NULL
AND SD.name in ('Voice over IP')
AND OP.resultingaction <> 2
AND OP.status = 10
AND ACC.status = 1
AND ismaxopid.id IS NULL
AND NOT EXISTS (SELECT 1
FROM OSQUESTION OSQ2
, ORDEREDSERVICE OS1
, OSPARAMDATACAPABILITY OSPARAMCAP1
, OSQUESTIONGROUP OSQGRP1
, ORDEREDPRODUCT OP3
where OSQ2.EXT_QUEST_ID = PD.ID
AND OSQ2.QUESTION_ID > OSQ.QUESTION_ID
AND OSQ2.PROVISIONED_VALUE = OSQ.CURRENT_VALUE
AND OSQ2.CURRENT_VALUE != OSQ.CURRENT_VALUE
AND PD.NAME IN ('Primary TN'
, 'VoIP MTA MAC address'
, 'HSDS CM MAC address')
AND OSQGRP1.QG_ID = OSQ2.QG_ID
AND OSPARAMCAP1.CAP_ID = OSQGRP1.CAP_ID
AND OS1.ID = OSPARAMCAP1.OS_ID
AND OP.ROOTPRODUCT_ID = OP3.ROOTPRODUCT_ID
AND OP3.ORDSERVICE_ID = OS1.ID
AND OP3.STATUS = 10)
ORDER BY ACC.EXTERNALBILLID
, OP.ROOTPRODUCT_ID
, CO.ID
的NOT EXISTS部分仍有待提高。
OTOH可以將「LEFT JOIN orderedproduct ismaxopid ON ismaxopid.product_id」重寫爲「NOT EXISTS」子查詢，該子查詢至少減少外部選擇的範圍表。其他「不存在」的東西看起來像是外部查詢（可能爲了清楚而被壓縮成視圖）中的一部分的常見子表達式。 – wildplasser
@wildplasser：我經歷過與非空檢查的左連接，大部分時間，導致更快的執行時間（我有一個查詢需要4秒，並重寫不存在的部分使它運行在3微秒）。 – Benoit
我在這裏看到「LEFT JOIN + NULL check」的成語。它似乎是一個{oracle，mysql}的東西。在Postgres中，它們導致完全相同的查詢計劃。 「不存在」更清晰，更可讀，恕我直言。 MAX（）也可以作爲一個集合來完成（+ - 集合的可空性） – wildplasser
首先識別查詢所有表中的所有PK字段。 然後根據oracle數據庫表中創建的PK字段的順序來更改where條件。
請參閱：http：//stackoverflow.com/questions/761204/what-resources-exist-for-database-performance-tuning和http://stackoverflow.com/questions/3706750/sql-tuning-in-oracle –
@yakub_moriss：也許一些不錯的縮進會吸引讀者。在目前的形式下，我不被它吸引。另外，我認爲導致這個查詢存在的人應該被槍殺。 – wildplasser
@catcall：美麗！你甚至修復了醜陋的相關名稱。 – wildplasser