我正在尝试优化一个以下解释计划的SQL。
我实际上是在解释计划中的这一特定行
45 NESTED LOOPS Cost: 782 Bytes: 293,832 Cardinality: 212
如果您注意到Bytes的数量是293K，并且由于它是嵌套循环，则最终SQL使用的缓冲区数量是数百万。 并且它被db profile阻止。
如何减少上面ROW 45的字节数的一般建议？
第45行注释（来自TOAD）：
对于步骤42检索的每一行，执行步骤44中的操作以找到匹配的行
非常感谢
SELECT STATEMENT HINT: ALL_ROWSCost: 800 Bytes: 7,844 Cardinality: 1
67 SORT ORDER BY Cost: 800 Bytes: 7,844 Cardinality: 1
66 VIEW VIEW SYS.VM_NWVW_2 Cost: 800 Bytes: 7,844 Cardinality: 1
65 HASH UNIQUE Cost: 800 Bytes: 1,672 Cardinality: 1
64 NESTED LOOPS OUTER Cost: 799 Bytes: 1,672 Cardinality: 1
61 NESTED LOOPS OUTER Cost: 795 Bytes: 1,627 Cardinality: 1
58 NESTED LOOPS OUTER Cost: 793 Bytes: 1,599 Cardinality: 1
55 NESTED LOOPS OUTER Cost: 791 Bytes: 1,571 Cardinality: 1
52 NESTED LOOPS OUTER Cost: 790 Bytes: 1,537 Cardinality: 1
49 NESTED LOOPS OUTER Cost: 788 Bytes: 1,491 Cardinality: 1
46 HASH JOIN Cost: 786 Bytes: 1,442 Cardinality: 1
2 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_POS_SKILL Cost: 4 Bytes: 56 Cardinality: 1
1 INDEX RANGE SCAN INDEX (UNIQUE) SIEBEL.S_POS_SKILL_U2 Cost: 3 Cardinality: 1
45 NESTED LOOPS Cost: 782 Bytes: 293,832 Cardinality: 212
42 NESTED LOOPS OUTER Cost: 722 Bytes: 4,056 Cardinality: 3
39 NESTED LOOPS OUTER Cost: 719 Bytes: 3,909 Cardinality: 3
36 HASH JOIN Cost: 716 Bytes: 3,795 Cardinality: 3
33 NESTED LOOPS Cost: 714 Bytes: 2,318 Cardinality: 2
30 NESTED LOOPS OUTER Cost: 710 Bytes: 1,662 Cardinality: 2
27 NESTED LOOPS OUTER Cost: 706 Bytes: 1,524 Cardinality: 2
24 NESTED LOOPS Cost: 704 Bytes: 1,316 Cardinality: 2
21 NESTED LOOPS Cost: 698 Bytes: 1,124 Cardinality: 2
18 NESTED LOOPS Cost: 696 Bytes: 984 Cardinality: 2
15 NESTED LOOPS Cost: 694 Bytes: 892 Cardinality: 2
12 NESTED LOOPS Cost: 692 Bytes: 660 Cardinality: 2
9 NESTED LOOPS Cost: 687 Bytes: 70 Cardinality: 1
6 NESTED LOOPS Cost: 5 Bytes: 49 Cardinality: 1
4 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_POSTN Cost: 4 Bytes: 37 Cardinality: 1
3 INDEX RANGE SCAN INDEX (UNIQUE) SIEBEL.S_POSTN_U1 Cost: 3 Cardinality: 1
5 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_PARTY_P1 Cost: 1 Bytes: 12 Cardinality: 1
8 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_OPTY_POSTN Cost: 682 Bytes: 21 Cardinality: 1
7 INDEX RANGE SCAN INDEX SIEBEL.S_OPTY_POSTN_M1 Cost: 6 Cardinality: 821
11 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_REVN Cost: 5 Bytes: 260 Cardinality: 1
10 INDEX RANGE SCAN INDEX SIEBEL.S_REVN_F3 Cost: 2 Cardinality: 6
14 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_PROD_LN Cost: 1 Bytes: 116 Cardinality: 1
13 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_PROD_LN_P1 Cost: 0 Cardinality: 1
17 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_USER Cost: 1 Bytes: 46 Cardinality: 1
16 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_USER_U2 Cost: 0 Cardinality: 1
20 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_POSTN Cost: 1 Bytes: 70 Cardinality: 1
19 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_POSTN_U2 Cost: 0 Cardinality: 1
23 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_REVN_X Cost: 3 Bytes: 96 Cardinality: 1
22 INDEX RANGE SCAN INDEX (UNIQUE) SIEBEL.S_REVN_X_U1 Cost: 2 Cardinality: 1
26 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_PROD_INT Cost: 2 Bytes: 104 Cardinality: 1
25 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_PROD_INT_P1 Cost: 1 Cardinality: 1
29 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_PROD_INT Cost: 2 Bytes: 69 Cardinality: 1
28 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_PROD_INT_P1 Cost: 1 Cardinality: 1
32 TABLE ACCESS BY GLOBAL INDEX ROWID TABLE SIEBEL.S_OPTY Cost: 2 Bytes: 328 Cardinality: 1 Partition #: 46 Partition access computed by row location
31 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_OPTY_P1 Cost: 1 Cardinality: 1
35 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_SALES_METHOD Cost: 1 Bytes: 318 Cardinality: 3
34 INDEX RANGE SCAN INDEX (UNIQUE) SIEBEL.S_SALES_METHOD_U1 Cost: 2 Cardinality: 1
38 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_STG Cost: 1 Bytes: 38 Cardinality: 1
37 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_STG_P1 Cost: 0 Cardinality: 1
41 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_POSTN Cost: 1 Bytes: 49 Cardinality: 1
40 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_POSTN_U2 Cost: 0 Cardinality: 1
44 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_POS_SKILL_IT Cost: 20 Bytes: 2,618 Cardinality: 77
43 INDEX RANGE SCAN INDEX SIEBEL.S_POS_SKILL_IT_F2 Cost: 2 Cardinality: 20
48 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_ORG_EXT Cost: 2 Bytes: 49 Cardinality: 1
47 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_ORG_EXT_P1 Cost: 1 Cardinality: 1
51 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_ORG_EXT Cost: 2 Bytes: 46 Cardinality: 1
50 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_ORG_EXT_U3 Cost: 1 Cardinality: 1
54 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_BU Cost: 1 Bytes: 34 Cardinality: 1
53 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_BU_P1 Cost: 0 Cardinality: 1
57 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_ORG_EXT Cost: 2 Bytes: 28 Cardinality: 1
56 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_ORG_EXT_U3 Cost: 1 Cardinality: 1
60 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_ORG_EXT Cost: 2 Bytes: 28 Cardinality: 1
59 INDEX UNIQUE SCAN INDEX (UNIQUE) SIEBEL.S_ORG_EXT_U3 Cost: 1 Cardinality: 1
63 TABLE ACCESS BY INDEX ROWID TABLE SIEBEL.S_OPTY_POSTN Cost: 4 Bytes: 450 Cardinality: 10
62 INDEX RANGE SCAN INDEX (UNIQUE) SIEBEL.S_OPTY_POSTN_U1 Cost: 3 Cardinality: 1
答案 0 :(得分：1)
真正的问题是以下几行：
8 INDEX ROWID表的访问权表SIEBEL.S_OPTY_POSTN成本：682字节：21基数：1 7 INDEX RANGE SCAN INDEX SIEBEL.S_OPTY_POSTN_M1成本：6基数：821
假设表/索引统计信息是最新的，它负责大部分成本。没有实际的sql语句，问题是为什么它更昂贵？
潜在问题：