我有一个类似于此的118行查询：
select * from (The inner query with many joins) WHERE campus_code IN ('560','598')
campus_code由内部查询中的函数f_get_bookstore(SSBSECT_TERM_CODE,SSBSECT_CRN) AS SSBSECT_CAMP_CODE生成。如果我单独运行内部查询，其计数为18＆amp;它将在13秒内执行。但是，如果我添加WHERE campus_code IN ('560','598')，则需要超过2分钟。
另一个奇怪的是，我有另一个查询，也像
select * from (The inner query with many joins) WHERE campus_code IN ('560','598')。这里的内部查询与前一个略有不同。内部查询很快＆amp;返回92行。但是这里campus_code IN过滤速度很快，即使它正在处理92行（与前一个查询的18行不同）。这里还通过相同的函数生成campus_code。
任何正文都可以帮助调整查询吗？请告诉您还需要更多信息。
这是整个查询：
SELECT *
FROM
(SELECT 'columbusstate' bk_institution_id,
'columbusstate.'
|| scbcrse_subj_code
|| '.'
|| scbcrse_crse_numb
||'.'
|| Ssbsect_Crn
|| '.'
|| ssbsect_term_code bk_section_id,
ssbsect_camp_code AS campus_code,
scbcrse_subj_code
|| '.'
|| scbcrse_crse_numb
||'.'
|| Ssbsect_Crn
|| '.'
|| ssbsect_term_code institution_section_id,
ssbsect_crn short_description,
scbcrse_title AS description,
ssbsect_crn sections_ssbsect_crn,
ssbsect_term_code sections_ssbsect_term_code,
'na' instructor_first_name,
'na' instructor_last_name,
scbcrse_subj_code
|| '.'
|| scbcrse_crse_numb rel_institution_course_id,
scbcrse_title AS rel_course_description,
scbcrse_title AS rel_course_name,
scbcrse_crse_numb AS course_short_desc,
scbcrse_crse_numb course_number,
stvterm_desc term_short_desc,
stvterm_code rel_institution_term_id,
section.ssbsect_crn,
ssbsect_ssts_code AS ssbsect_ssts_code,
'columbusstate.'
|| stvterm_code rel_bk_term_id,
'columbusstate.'
|| scbcrse_subj_code
|| '.'
|| scbcrse_crse_numb rel_bk_course_id,
ssbsect_seq_numb,
ssbsect_enrl ssbsect_enrl,
ssbsect_enrl estimated_enrl,
ssbsect_max_enrl ssbsect_max_enrl,
ssbsect_crn ssbsect_section_key,
ssbsect_crn ssbsect_section_number,
'parent' relationship,
course.scbcrse_subj_code institution_department_id ,
'DFLT' institution_division_id,
'DFLT' division_short_desc
FROM
(SELECT *
FROM
(SELECT SSBSECT_TERM_CODE,
SSBSECT_CRN,
SSBSECT_SUBJ_CODE,
SSBSECT_CRSE_NUMB,
SSBSECT_PTRM_CODE,
SSBSECT_SEQ_NUMB,
SSBSECT_SSTS_CODE,
SSBSECT_MAX_ENRL,
SSBSECT_ENRL,
SSBSECT_PRNT_IND,
f_get_bookstore(SSBSECT_TERM_CODE,SSBSECT_CRN) AS SSBSECT_CAMP_CODE
FROM SSBSECT
) sect
JOIN
(SELECT *
FROM
(SELECT * FROM saturn.stvterm WHERE STVTERM_CODE >= '201401'
)
) term
ON term.stvterm_code=sect.ssbsect_term_code
) section
JOIN
(SELECT C1.scbcrse_subj_code,
C1.scbcrse_dept_code,
C1.scbcrse_crse_numb,
C1.scbcrse_title
FROM saturn.scbcrse C1
LEFT JOIN saturn.scbcrse C2
ON (C1.scbcrse_subj_code = C2.scbcrse_subj_code
AND C1.scbcrse_crse_numb = C2.scbcrse_crse_numb
AND C1.scbcrse_eff_term < C2.scbcrse_eff_term)
WHERE c2.scbcrse_eff_term IS NULL
) Course ON Course.scbcrse_subj_code = Section.ssbsect_subj_code
AND scbcrse_crse_numb = section.ssbsect_crse_numb
AND ssbsect_ssts_code IN ('A','V','X')
LEFT JOIN
(SELECT sirasgn_term_code sirasgn_term_code,
sirasgn_crn,
MAX(spriden_pidm) spriden_pidm,
MAX(spriden_first_name) instructor_first_name,
MAX(spriden_last_name) instructor_last_name
FROM
(SELECT Pidm spriden_pidm,
Csu_Id SPRIDEN_ID,
First_Name spriden_first_name,
Last_Name spriden_last_name,
Mi spriden_mi,
External_User_Id login,
Email
FROM Csuapps.Wfollett_Person
) persons
JOIN
( SELECT * FROM saturn.sirasgn WHERE SIRASGN_PRIMARY_IND = 'Y'
) relations
ON persons.spriden_pidm=relations.sirasgn_pidm
GROUP BY sirasgn_crn,
sirasgn_term_code
) instr ON section.ssbsect_term_code=instr.sirasgn_term_code
AND section.ssbsect_crn =instr.sirasgn_crn
WHERE Course.scbcrse_subj_code = 'ACCT'
AND section.ssbsect_term_code = '201702'
)
WHERE campus_code IN ('560','1157')
执行计划：
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 2063389120
-----------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)| Time |
-----------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 77 | 968K| | 4364 (3)| 00:00:01 |
| 1 | SORT ORDER BY | | 77 | 968K| 624K| 4364 (3)| 00:00:01 |
|* 2 | VIEW | | 77 | 968K| | 4155 (3)| 00:00:01 |
| 3 | COUNT | | | | | | |
| 4 | VIEW | | 77 | 967K| | 4155 (3)| 00:00:01 |
| 5 | SORT ORDER BY | | 77 | 774K| | 4155 (3)| 00:00:01 |
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|* 6 | FILTER | | | | | | |
|* 7 | HASH JOIN RIGHT OUTER | | 77 | 774K| | 4154 (3)| 00:00:01 |
|* 8 | INDEX RANGE SCAN | SCBCRSE_KEY_INDEX | 83 | 1494 | | 1 (0)| 00:00:01 |
| 9 | NESTED LOOPS | | 77 | 772K| | 4153 (3)| 00:00:01 |
| 10 | NESTED LOOPS OUTER | | 23 | 229K| | 4139 (3)| 00:00:01 |
|* 11 | HASH JOIN OUTER | | 23 | 1656 | | 3783 (1)| 00:00:01 |
| 12 | NESTED LOOPS | | 23 | 1334 | | 7 (0)| 00:00:01 |
| 13 | TABLE ACCESS BY INDEX ROWID | STVTERM | 1 | 22 | | 1 (0)| 00:00:01 |
|* 14 | INDEX UNIQUE SCAN | PK_STVTERM | 1 | | | 1 (0)| 00:00:01 |
|* 15 | TABLE ACCESS BY INDEX ROWID BATCHED| SSBSECT | 23 | 828 | | 6 (0)| 00:00:01 |
|* 16 | INDEX RANGE SCAN | SSBSECT_INDEX_SUBJ | 25 | | | 1 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| 17 | VIEW | | 2172 | 30408 | | 3775 (1)| 00:00:01 |
| 18 | HASH GROUP BY | | 2172 | 8537K| 16M| 3775 (1)| 00:00:01 |
|* 19 | HASH JOIN | | 4166 | 15M| | 1364 (1)| 00:00:01 |
| 20 | VIEW | VW_GBF_14 | 2312 | 18496 | | 211 (1)| 00:00:01 |
| 21 | HASH GROUP BY | | 2312 | 48552 | | 211 (1)| 00:00:01 |
|* 22 | TABLE ACCESS FULL | SIRASGN | 2312 | 48552 | | 210 (1)| 00:00:01 |
| 23 | VIEW | WFOLLETT_PERSON | 3714 | 14M| | 1153 (1)| 00:00:01 |
| 24 | SORT UNIQUE | | 3714 | 342K| | 1153 (1)| 00:00:01 |
| 25 | UNION-ALL | | | | | | |
| 26 | NESTED LOOPS | | 1 | 59 | | 2 (0)| 00:00:01 |
| 27 | NESTED LOOPS | | 1 | 59 | | 2 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|* 28 | INDEX RANGE SCAN | PK_GLBEXTR | 1 | 38 | | 1 (0)| 00:00:01 |
|* 29 | INDEX UNIQUE SCAN | PK_GOBTPAC | 1 | | | 1 (0)| 00:00:01 |
| 30 | TABLE ACCESS BY INDEX ROWID | GOBTPAC | 1 | 21 | | 1 (0)| 00:00:01 |
| 31 | NESTED LOOPS | | 1912 | 130K| | 605 (0)| 00:00:01 |
| 32 | NESTED LOOPS | | 1912 | 130K| | 605 (0)| 00:00:01 |
|* 33 | HASH JOIN | | 1912 | 93688 | | 31 (0)| 00:00:01 |
| 34 | VIEW | VW_SQ_2 | 3076 | 83052 | | 10 (0)| 00:00:01 |
| 35 | HASH GROUP BY | | 3076 | 39988 | | 10 (0)| 00:00:01 |
| 36 | INDEX FULL SCAN | PK_SIBINST | 6243 | 81159 | | 10 (0)| 00:00:01 |
|* 37 | TABLE ACCESS FULL | SIBINST | 3881 | 85382 | | 21 (0)| 00:00:01 |
|* 38 | INDEX UNIQUE SCAN | PK_GOBTPAC | 1 | | | 1 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| 39 | TABLE ACCESS BY INDEX ROWID | GOBTPAC | 1 | 21 | | 1 (0)| 00:00:01 |
| 40 | NESTED LOOPS | | 1801 | 41423 | | 543 (1)| 00:00:01 |
| 41 | NESTED LOOPS | | 1801 | 41423 | | 543 (1)| 00:00:01 |
| 42 | VIEW | VW_DTP_6100A9C4 | 1801 | 3602 | | 3 (34)| 00:00:01 |
| 43 | HASH UNIQUE | | 1801 | 23413 | | 3 (34)| 00:00:01 |
|* 44 | INDEX RANGE SCAN | PK_SIRASGN | 4161 | 54093 | | 2 (0)| 00:00:01 |
|* 45 | INDEX UNIQUE SCAN | PK_GOBTPAC | 1 | | | 1 (0)| 00:00:01 |
| 46 | TABLE ACCESS BY INDEX ROWID | GOBTPAC | 1 | 21 | | 1 (0)| 00:00:01 |
| 47 | VIEW PUSHED PREDICATE | | 1 | 10165 | | 16 (25)| 00:00:01 |
|* 48 | FILTER | | | | | | |
| 49 | NESTED LOOPS | | 1 | 10164 | | 16 (25)| 00:00:01 |
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| 50 | NESTED LOOPS | | 1 | 79 | | 4 (0)| 00:00:01 |
|* 51 | FILTER | | | | | | |
| 52 | NESTED LOOPS OUTER | | 1 | 60 | | 3 (0)| 00:00:01 |
| 53 | NESTED LOOPS | | 1 | 42 | | 2 (0)| 00:00:01 |
| 54 | TABLE ACCESS BY INDEX ROWID | SSBSECT | 1 | 24 | | 1 (0)| 00:00:01 |
|* 55 | INDEX UNIQUE SCAN | PK_SSBSECT | 1 | | | 1 (0)| 00:00:01 |
|* 56 | INDEX RANGE SCAN | SCBCRSE_KEY_INDEX | 1 | 18 | | 1 (0)| 00:00:01 |
|* 57 | INDEX RANGE SCAN | SCBCRSE_KEY_INDEX | 15046 | 264K| | 1 (0)| 00:00:01 |
|* 58 | INDEX RANGE SCAN | PK_SIRASGN | 1 | 19 | | 1 (0)| 00:00:01 |
| 59 | VIEW | WFOLLETT_PERSON | 1 | 10085 | | 12 (34)| 00:00:01 |
| 60 | SORT UNIQUE | | 3 | 304 | | 12 (34)| 00:00:01 |
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| 61 | UNION ALL PUSHED PREDICATE | | | | | | |
| 62 | NESTED LOOPS | | 1 | 59 | | 2 (0)| 00:00:01 |
| 63 | TABLE ACCESS BY INDEX ROWID | GOBTPAC | 1 | 21 | | 1 (0)| 00:00:01 |
|* 64 | INDEX UNIQUE SCAN | PK_GOBTPAC | 1 | | | 1 (0)| 00:00:01 |
|* 65 | INDEX RANGE SCAN | PK_GLBEXTR | 1 | 38 | | 1 (0)| 00:00:01 |
| 66 | NESTED LOOPS | | 1 | 70 | | 3 (0)| 00:00:01 |
| 67 | NESTED LOOPS | | 1 | 70 | | 3 (0)| 00:00:01 |
| 68 | NESTED LOOPS | | 1 | 48 | | 2 (0)| 00:00:01 |
| 69 | TABLE ACCESS BY INDEX ROWID | GOBTPAC | 1 | 21 | | 1 (0)| 00:00:01 |
|* 70 | INDEX UNIQUE SCAN | PK_GOBTPAC | 1 | | | 1 (0)| 00:00:01 |
| 71 | VIEW | VW_SQ_1 | 1 | 27 | | 1 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| 72 | SORT GROUP BY | | 1 | 13 | | 1 (0)| 00:00:01 |
|* 73 | INDEX RANGE SCAN | PK_SIBINST | 2 | 26 | | 1 (0)| 00:00:01 |
|* 74 | INDEX UNIQUE SCAN | PK_SIBINST | 1 | | | 1 (0)| 00:00:01 |
|* 75 | TABLE ACCESS BY INDEX ROWID | SIBINST | 1 | 22 | | 1 (0)| 00:00:01 |
| 76 | NESTED LOOPS | | 1 | 23 | | 4 (25)| 00:00:01 |
| 77 | TABLE ACCESS BY INDEX ROWID | GOBTPAC | 1 | 21 | | 1 (0)| 00:00:01 |
|* 78 | INDEX UNIQUE SCAN | PK_GOBTPAC | 1 | | | 1 (0)| 00:00:01 |
|* 79 | VIEW | VW_DTP_32C68FB6 | 1 | 2 | | 3 (34)| 00:00:01 |
| 80 | SORT UNIQUE | | 2 | 26 | | 3 (34)| 00:00:01 |
|* 81 | INDEX RANGE SCAN | PK_SIRASGN | 2 | 26 | | 2 (0)| 00:00:01 |
| 82 | TABLE ACCESS BY INDEX ROWID BATCHED | SCBCRSE | 3 | 126 | | 1 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|* 83 | INDEX RANGE SCAN | SCBCRSE_KEY_INDEX | 1 | | | 1 (0)| 00:00:01 |
-----------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter(("from$_subquery$_002"."CAMPUS_CODE"='1157' OR "from$_subquery$_002"."CAMPUS_CODE"='560') AND "R">=1
AND "R"<=1500)
6 - filter("C2"."SCBCRSE_EFF_TERM" IS NULL)
7 - access("C1"."SCBCRSE_SUBJ_CODE"="C2"."SCBCRSE_SUBJ_CODE"(+) AND
"C1"."SCBCRSE_CRSE_NUMB"="C2"."SCBCRSE_CRSE_NUMB"(+))
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
filter("C1"."SCBCRSE_EFF_TERM"<"C2"."SCBCRSE_EFF_TERM"(+))
8 - access("C2"."SCBCRSE_SUBJ_CODE"(+)='ACCT')
11 - access("SSBSECT_TERM_CODE"="INSTR"."SIRASGN_TERM_CODE"(+) AND "SSBSECT_CRN"="INSTR"."SIRASGN_CRN"(+))
14 - access("STVTERM"."STVTERM_CODE"='201702')
15 - filter("SSBSECT_SSTS_CODE"='A' OR "SSBSECT_SSTS_CODE"='V' OR "SSBSECT_SSTS_CODE"='X')
16 - access("SSBSECT_SUBJ_CODE"='ACCT' AND "SSBSECT_TERM_CODE"='201702')
filter("SSBSECT_TERM_CODE"='201702')
19 - access("PIDM"="ITEM_1")
22 - filter("SIRASGN"."SIRASGN_TERM_CODE"='201702' AND "SIRASGN_PRIMARY_IND"='Y')
28 - access("GLBEXTR_APPLICATION"='STUDENT' AND "GLBEXTR_SELECTION"='CURR_ENRL' AND "GLBEXTR_CREATOR_ID"='GSHOUL')
29 - access("GOBTPAC_PIDM"=TO_NUMBER("GLBEXTR_KEY"))
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
33 - access("A"."SIBINST_TERM_CODE_EFF"="MAX(B.SIBINST_TERM_CODE_EFF)" AND "ITEM_2"="A"."SIBINST_PIDM")
37 - filter("A"."SIBINST_FCST_CODE"='AC' AND "A"."SIBINST_FCTG_CODE"<>'EMPL')
38 - access("A"."SIBINST_PIDM"="GOBTPAC_PIDM")
44 - access("SIRASGN_TERM_CODE">="TOOLS"."GETTERMCODE"(NULL,SYSDATE@!))
45 - access("ITEM_1"="GOBTPAC_PIDM")
48 - filter("SSBSECT_TERM_CODE">='201602' AND "SSBSECT_TERM_CODE"='201702')
51 - filter("C2"."SCBCRSE_EFF_TERM" IS NULL)
55 - access("SSBSECT_TERM_CODE"="SSBSECT_TERM_CODE" AND "SSBSECT_CRN"="SSBSECT_CRN")
filter("SSBSECT_TERM_CODE"='201702')
56 - access("SSBSECT_SUBJ_CODE"="C1"."SCBCRSE_SUBJ_CODE" AND "SSBSECT_CRSE_NUMB"="C1"."SCBCRSE_CRSE_NUMB")
57 - access("C1"."SCBCRSE_SUBJ_CODE"="C2"."SCBCRSE_SUBJ_CODE"(+) AND
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
"C1"."SCBCRSE_CRSE_NUMB"="C2"."SCBCRSE_CRSE_NUMB"(+) AND "C1"."SCBCRSE_EFF_TERM"<"C2"."SCBCRSE_EFF_TERM"(+) AND
"C2"."SCBCRSE_EFF_TERM"(+) IS NOT NULL)
58 - access("REL"."SIRASGN_TERM_CODE"="SSBSECT_TERM_CODE" AND "REL"."SIRASGN_CRN"="SSBSECT_CRN")
filter("REL"."SIRASGN_TERM_CODE"="SSBSECT_TERM_CODE" AND "REL"."SIRASGN_TERM_CODE"='201702' AND
"REL"."SIRASGN_CRN"="SSBSECT_CRN")
64 - access("GOBTPAC_PIDM"="REL"."SIRASGN_PIDM")
65 - access("GLBEXTR_APPLICATION"='STUDENT' AND "GLBEXTR_SELECTION"='CURR_ENRL' AND "GLBEXTR_CREATOR_ID"='GSHOUL')
filter(TO_NUMBER("GLBEXTR_KEY")="REL"."SIRASGN_PIDM" AND "GOBTPAC_PIDM"=TO_NUMBER("GLBEXTR_KEY"))
70 - access("GOBTPAC_PIDM"="REL"."SIRASGN_PIDM")
73 - access("B"."SIBINST_PIDM"="REL"."SIRASGN_PIDM")
74 - access("A"."SIBINST_PIDM"="REL"."SIRASGN_PIDM" AND "A"."SIBINST_TERM_CODE_EFF"="MAX(B.SIBINST_TERM_CODE_EFF)")
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
filter("A"."SIBINST_PIDM"="GOBTPAC_PIDM" AND "ITEM_1"="A"."SIBINST_PIDM")
75 - filter("A"."SIBINST_FCST_CODE"='AC' AND "A"."SIBINST_FCTG_CODE"<>'EMPL')
78 - access("GOBTPAC_PIDM"="REL"."SIRASGN_PIDM")
79 - filter("ITEM_1"="GOBTPAC_PIDM")
81 - access("SIRASGN_TERM_CODE">="TOOLS"."GETTERMCODE"(NULL,SYSDATE@!) AND "SIRASGN_PIDM"="REL"."SIRASGN_PIDM")
filter("SIRASGN_PIDM"="REL"."SIRASGN_PIDM")
83 - access("C1"."SCBCRSE_SUBJ_CODE"='ACCT' AND "C1"."SCBCRSE_CRSE_NUMB"="SSBSECT_CRSE_NUMB")
139 rows selected.
答案 0 :(得分：2)
您的查询的效果取决于我们不了解的详细信息以及联接。通常，如果连接导致一组巨大的行，那将会占用大量的cpu和ram。因此，请尝试添加where子句，以最小化连接中的行数。
另一方面说，想象一下你是cpu。浏览您的查询并尝试估算您需要处理的行数，以及如何限制该行数。
您是否在关键表上使用索引来加速选择？您是否正在修改索引中使用的搜索列，以使索引不起作用？像这样的东西非常重要。
祝你好运！更新
该计划告诉我，大多数cpu都是针对最外层查询进行刻录的，这是您在时序测量中已经注意到的。我的策略是尝试将最外层的where子句移向内部查询。如果数据库引擎可以在早期阶段应用where子句，则查询将需要更少的内存和cpu。
现在无法查看每个输出字段属于哪个表。如果我在哪里，我会在每个FROM别名中给每个表。
为了测试性能以及在此处发布，您可以简化输出字段列表。省去外部查询不需要的字段，或使用星号。此外，尝试呈现一个完美的印刷查询。
除了计划之外，你能获得一些关于内存使用情况的信息吗？使用外部查询，可能需要在输出结果之前在内存中获取大量数据。试想一下，如果这会导致内存耗尽并需要交换，那将耗费大量时间。内存使用也可能来自锁定可能的大桌子，所以不要被你的“仅18行”愚弄。输出。
答案 1 :(得分：1)
好的，我打算把它放在“答案”中，因为评论似乎被忽略了。
了解正在发生的事情以及如何解决问题的唯一方法是获取执行计划。否则每个答案都是猜测。你可能会很幸运，猜测有效，但你永远不会知道为什么。所以请帮助我们帮助你。
要获得执行计划（对于包含和不包含WHERE子句的查询），请在查询后运行此...
set lines 500
set pages 10000
select * from table( dbms_xplan.display_cursor( null, null, 'TYPICAL' ));
答案 2 :(得分：0)
campus_code是整数吗？如果是，请尝试删除撇号，如下所示：
WHERE campus_code IN (560,598)
否则，每个值在被比较之前都会被转换，这可能会花费很多时间。
希望这有帮助。
答案 3 :(得分：0)
您观察到的是内联视图中99％的合并谓词。
这通常很好，有助于提高性能，如下例所示。
示例数据
create table T1 as
select 'xxxx'||rownum crampus_code from dual connect by level <= 100000;
create index idx1 on t1(crampus_code);
由于必须访问整个表，因此此查询可能需要在大型表上花费大量时间。
select crampus_code, count(*) from T1 group by crampus_code;
以下查询使用上一个查询作为子查询可能非常有效。怎么样？
子查询中WHERE中的MERGE子句，只访问（索引）和聚合两个键的数据。
with agg as
(
select
a.crampus_code, count(*)
from
T1 a
group by
crampus_code
)
select *
from agg
where crampus_code in ('xxxx42','xxxx399');
证据在执行计划中（您未提供）
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 2 | 48 | 3 (0)| 00:00:01 |
| 1 | SORT GROUP BY NOSORT| | 2 | 48 | 3 (0)| 00:00:01 |
| 2 | INLIST ITERATOR | | | | | |
|* 3 | INDEX RANGE SCAN | IDX1 | 2 | 48 | 3 (0)| 00:00:01 |
-----------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("A"."CRAMPUS_CODE"='xxxx399' OR
"A"."CRAMPUS_CODE"='xxxx42')
您看到表只能通过索引访问两个键。
您的案例
这只是推测，但IMO在合并谓词阶段你会得到一个更糟糕的执行计划，没有它。
这解释了加入WHERE子句后经过的时间的增加。
只有当您同时显示两个计划（子查询和WHERE查询）时，您才能确定...
解决方法
那么，如果谓词合并破坏了性能，你会怎么做？
简单地将其关闭。不幸的是，您必须使用未记录的提示MATERIALIZE，将查询结果设置为临时表 并且将在其上应用WHERE谓词。
这适用于18行。我不确定，但你必须使用子查询因子（WITH）重写查询。
with agg as
(select /*+ MATERIALIZE */ a.crampus_code, count(*) from T1 a group by crampus_code)
select * from agg
where crampus_code in ('xxxx42','xxxx399');
----------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 97325 | 3516K| 94 (5)| 00:00:02 |
| 1 | TEMP TABLE TRANSFORMATION | | | | | |
| 2 | LOAD AS SELECT | SYS_TEMP_0FD9D673A_CE046F62 | | | | |
| 3 | HASH GROUP BY | | 97325 | 2281K| 41 (10)| 00:00:01 |
| 4 | TABLE ACCESS FULL | T1 | 97325 | 2281K| 37 (0)| 00:00:01 |
|* 5 | VIEW | | 97325 | 3516K| 54 (2)| 00:00:01 |
| 6 | TABLE ACCESS FULL | SYS_TEMP_0FD9D673A_CE046F62 | 97325 | 2281K| 54 (2)| 00:00:01 |
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Predicate Information (identified by operation id):
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5 - filter("CRAMPUS_CODE"='xxxx399' OR "CRAMPUS_CODE"='xxxx42')