ORACLE中关于外键缺少索引的探讨和总结
作者：潇湘隐者
在ORACLE数据库中，定义外键约束时，ORACLE是不会自动创建对应索引的，必须手动在外键约束相关的列上创建索引。那么外键字段上是否有必要创建索引呢？如果有必要的话，巡检时，如何找出外键字段上没有创建索引的相关表，并生成对应的索引的脚本呢？
外键缺失索引影响
外键列上缺少索引会带来三个问题，限制并发性、影响性能、还有可能造成死锁。所以对于绝大部分场景，我们应该尽量考虑在外键上面创建索引
影响性能。 如果子表外键没有创建索引，那么当父表查询关联子表时，子表将进行全表扫描。影响表连接方式。
影响并发。 无论是更新父表主键，或者删除一个父记录，都会在子表中加一个表锁（在这条语句完成前，不允许对子表做任何修改）。这就会不必要
地锁定更多的行，而影响并发性
3：在特殊情况下，还有可能造成死锁。
我们先来看看一个简单的例子，看看当外键缺失索引时，子表是否进行全表扫描，如下所示，表EMP与DEPT存在主外键关系：
SQL> set autotrace on;
SQL>
SQL> SELECT D.DEPTNO, COUNT(*)
2 FROM SCOTT.EMP E INNER JOIN SCOTT.DEPT D ON E.DEPTNO =D.DEPTNO
3 GROUP BY D.DEPTNO;
DEPTNO COUNT(*)
---------- ----------
30 6
20 5
10 3
Execution Plan
----------------------------------------------------------
Plan hash value: 4067220884
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 3 | 9 | 4 (25)| 00:00:01 |
| 1 | HASH GROUP BY | | 3 | 9 | 4 (25)| 00:00:01 |
|* 2 | TABLE ACCESS FULL| EMP | 14 | 42 | 3 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter("E"."DEPTNO" IS NOT NULL)
Statistics
----------------------------------------------------------
1 recursive calls
0 db block gets
7 consistent gets
0 physical reads
0 redo size
665 bytes sent via SQL*Net to client
524 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
3 rows processed
如上所示，当外键字段没有索引时，父表与子表关联时，子表会进行全表扫描，下面，我在外键字段创建索引后，就能避免子表表扫描了。
CREATE INDEX SCOTT.IX_DEPTNO ON SCOTT.EMP (“DEPTNO”) TABLESPACE USERS; 
当然这两个表的数据量实在是太少了，性能上差别不大，当数据量增长上去后，这个性能差异就会比较明显了。如下例子所示，我们构造一个数据量相对较大的父表与子表：
create table parent_tb_test
(
id number(10),
name varchar2(32),
constraint pk_parent_tb_test primary key(id)
);
create table child_tb_test
(
c_id number(10),
f_id number(10),
child_name varchar2(32),
constraint pk_child_tb_test primary key(c_id),
foreign key(f_id) references parent_tb_test
);
begin
for index_num in 1 .. 10000 loop
insert into parent_tb_test
select index_num , 'kerry' || to_char(index_num) from dual;
if mod(index_num,100) = 0 then
commit;
end if;
end loop;
commit;
end;
/
declare index_num number :=1;
begin
for index_parent in 1 .. 10000 loop
for index_child in 1 .. 1000 loop
insert into child_tb_test
select index_num, index_parent, 'child' || to_char(index_child) from dual;
index_num := index_num +1;
if mod(index_child,1000) = 0 then
commit;
end if;
end loop;
end loop;
commit;
end;
/
SQL> execute dbms_stats.gather_table_stats(ownname => 'TEST', tabname =>'PARENT_TB_TEST', estimate_percent =>DBMS_STATS.AUTO_SAMPLE_SIZE, method_opt => 'FOR ALL COLUMNS SIZE AUTO');
PL/SQL procedure successfully completed.
SQL> execute dbms_stats.gather_table_stats(ownname => 'TEST', tabname =>'CHILD_TB_TEST', estimate_percent =>DBMS_STATS.AUTO_SAMPLE_SIZE, method_opt => 'FOR ALL COLUMNS SIZE AUTO');
PL/SQL procedure successfully completed.
SQL>上面脚本构造了测试用的例子和数据， 那么我们对比看看外键有无索引的区别：
SQL> set linesize 1200
SQL> set autotrace traceonly
SQL> select p.id , p.name,c.child_name
2 from test.parent_tb_test p
3 inner join test.child_tb_test c on p.id = c.f_id
4 where p.id=1000;
1000 rows selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 901213199
--------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1009 | 44396 | 4706 (21)| 00:00:07 |
| 1 | NESTED LOOPS | | 1009 | 44396 | 4706 (21)| 00:00:07 |
| 2 | TABLE ACCESS BY INDEX ROWID| PARENT_TB_TEST | 1 | 31 | 1 (0)| 00:00:01 |
|* 3 | INDEX UNIQUE SCAN | PK_PARENT_TB_TEST | 1 | | 1 (0)| 00:00:01 |
|* 4 | TABLE ACCESS FULL | CHILD_TB_TEST | 1009 | 13117 | 4705 (21)| 00:00:07 |
--------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("P"."ID"=1000)
4 - filter("C"."F_ID"=1000)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
32855 consistent gets
32772 physical reads
0 redo size
29668 bytes sent via SQL*Net to client
1218 bytes received via SQL*Net from client
68 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1000 rows processed
SQL> 
创建索引后，我们再来看看其执行计划，注意对比创建索引前后，执行计划的差异，如下所示：
SQL> create index ix_child_tb_test on child_tb_test(f_id);
SQL> set linesize 1200
SQL> set autotrace traceonly
SQL> select p.id , p.name,c.child_name
2 from test.parent_tb_test p
3 inner join test.child_tb_test c on p.id = c.f_id
4 where p.id=1000;
接下来，我们再来看看外键缺失索引影响并发，以及造成死锁的情况，如下所示，创建表dead_lock_parent与dead_lock_foreign，两者存在主外键关系，分布插入两条测试数据：
SQL> create table dead_lock_parent( id number primary key, name varchar2(32));
Table created.
SQL> create table dead_lock_foreign(fid number, fname varchar2(32), foreign key(fid) references dead_lock_parent);
Table created.
SQL> insert into dead_lock_parent values( 1, 'kerry');
1 row created.
SQL> insert into dead_lock_foreign values(1, 'kerry_fk');
1 row created.
SQL> insert into dead_lock_parent values(2, 'jimmy');
1 row created.
SQL> insert into dead_lock_foreign values(2, 'jimmy_fk');
1 row created.
SQL> commit;
Commit complete.
SQL> 1：在会话1（会话ID为789）里面执行下面SQL语句：
SQL> show user;
USER 为 "TEST"
SQL> select * from v$mystat where rownum=1;
SID STATISTIC# VALUE
---------- ---------- ----------
789 0 1
SQL> delete from dead_lock_foreign where fid=1;
已删除 1 行。2：在会话2（会话ID为766）里面执行下面SQL语句：
SQL> show user;
USER is "TEST"
SQL> select * from v$mystat where rownum=1;
SID STATISTIC# VALUE
---------- ---------- ----------
766 0 1
SQL> delete from dead_lock_foreign where fid=2;
1 row deleted.3：接着在会话1（会话ID为789）里执行删除dead_lock_parent中id为1的记录：
SQL> delete from dead_lock_parent where id=1;此时你会发现会话被阻塞了，我们可以用下面SQL查询具体的阻塞信息。
COL MODE_HELD FOR A14;
COL LOCK_TYPE FOR A8;
COL MODE_REQUESTED FOR A10;
COL OBJECT_TYPE FOR A14;
COL OBJECT_NAME FOR A20;
SELECT LK.SID,
DECODE(LK.TYPE,
'TX',
'Transaction',
'TM',
'DML',
'UL',
'PL/SQL User Lock',
LK.TYPE) LOCK_TYPE,
DECODE(LK.LMODE,
0,
'None',
1,
'Null',
2,
'Row-S (SS)',
3,
'Row-X (SX)',
4,
'Share',
5,
'S/Row-X (SSX)',
6,
'Exclusive',
TO_CHAR(LK.LMODE)) MODE_HELD,
DECODE(LK.REQUEST,
0,
'None',
1,
'Null',
2,
'Row-S (SS)',
3,
'Row-X (SX)',
4,
'Share',
5,
'S/Row-X (SSX)',
6,
'Exclusive',
TO_CHAR(LK.REQUEST)) MODE_REQUESTED,
OB.OBJECT_TYPE,
OB.OBJECT_NAME,
LK.BLOCK,
SE.LOCKWAIT
FROM V$LOCK LK, DBA_OBJECTS OB, V$SESSION SE
WHERE LK.TYPE IN ('TM', 'UL')
AND LK.SID = SE.SID
AND LK.ID1 = OB.OBJECT_ID(+)
AND SE.SID IN (766,789)
ORDER BY SID;
上面信息如果不能让你理解，那么可以看看下面脚本，相信你能看得更详细。
SQL> SELECT S.SID SID,
S.USERNAME USERNAME,
S.MACHINE MACHINE,
L.TYPE TYPE,
O.OBJECT_NAME OBJECT_NAME,
DECODE(L.LMODE, 0, 'None',
1, 'Null',
2, 'Row Share',
3, 'Row Exlusive',
4, 'Share',
5, 'Sh/Row Exlusive',
6, 'Exclusive') lmode,
DECODE(L.REQUEST, 0, 'None',
1, 'Null',
2, 'Row Share',
3, 'Row Exlusive',
4, 'Share',
5, 'Sh/Row Exlusive',
6, 'Exclusive') request,
L.BLOCK BLOCK
FROM V$LOCK L,
V$SESSION S,
DBA_OBJECTS O
WHERE L.SID = S.SID
AND USERNAME != 'SYSTEM'
AND O.OBJECT_ID(+) = L.ID1
AND S.SID IN ( 766,789)
ORDER BY S.SID;
SID USERNAME MACHINE TY OBJECT_NAME LMODE REQUEST BLOCK
---------- -------- -------------- -- -------------------- --------------- --------------- -----
766 TEST XXXX\GET253194 TX Exclusive None 0
766 TEST XXXX\GET253194 TM DEAD_LOCK_FOREIGN Row Exlusive None 1
766 TEST XXXX\GET253194 TM DEAD_LOCK_PARENT Row Exlusive None 0
883 TEST DB-Server.loca TX Exclusive None 0
ldomain
883 TEST DB-Server.loca TM DEAD_LOCK_PARENT Row Exlusive None 0
ldomain
883 TEST DB-Server.loca TM DEAD_LOCK_FOREIGN Row Exlusive Sh/Row Exlusive 0
ldomain 接着在会话2里面执行下面SQL，删除主表中id=2的记录
SQL> delete from dead_lock_parent where id=2;你会发现会话1就会出现Deadlock 
如果你在外键字段上创建索引，那么这种情况下的操作就不会出现死锁。在这里就不再赘述。有兴趣可以测试一下.
外键创建索引建议（Foreign Key Indexing Tips）
虽然增加索引，可能会带来一些额外的性能开销（DML操作开销增加）和磁盘空间方面的开销，但是相比其带来的性能改善而言，这些额外的开销其实完全可以忽略。如果没有其他特殊情况，建议所有的外键字段都加上索引。在Oracle Oracle Database 9i/10g/11g编程艺术这本书中介绍了在什么时候不需要对外键加索引. 必须满足下面三个条件：
1: 不会删除父表中的行。
2： 不论是有意还是无意，总之不会更新父表的唯一/主键字段值。
3： 不会从父表联结到子表， 或者更通俗的讲，外键列不支持子表的一个重要访问路径，而且你在谓词中没有使用这些外键累从子表中选择数据。
找出未索引的外键
我们首先可以通过下面脚本，找到整个数据库中那些表有主外键关系，并列出主外键约束.
–查看整个数据库下拥有主外键关系的所有表（排除一些系统用户）
--查看整个数据库下拥有主外键关系的所有表（排除一些系统用户）
SELECT DC.OWNER AS "PARENT_TABLE_OWNER",
DC.TABLE_NAME AS "PARENT_TABLE_NAME",
DC.CONSTRAINT_NAME AS "PRIMARY CONSTRAINT NAME",
DF.CONSTRAINT_NAME AS "REFERENCED CONSTRAINT NAME",
DF.OWNER AS "CHILD_TABLE_OWNER",
DF.TABLE_NAME AS "CHILD_TABLE_NAME"
FROM DBA_CONSTRAINTS DC,
(SELECT C.OWNER,
C.CONSTRAINT_NAME,
C.R_CONSTRAINT_NAME,
C.TABLE_NAME
FROM DBA_CONSTRAINTS C
WHERE CONSTRAINT_TYPE = 'R') DF
WHERE DC.CONSTRAINT_NAME =DF.R_CONSTRAINT_NAME
AND DC.OWNER NOT IN ( 'SYSTEM', 'SYS', 'DBSNMP', 'EXFSYS',
'ORDDATA', 'CTXSYS', 'OLAPSYS', 'MDSYS',
'SYSMAN' ); –查看某个Schema下拥有主外键关系的所有表
--查看某个Schema下拥有主外键关系的所有表
SELECT DC.OWNER AS "PARENT_TABLE_OWNER",
DC.TABLE_NAME AS "PARENT_TABLE_NAME",
DC.CONSTRAINT_NAME AS "PRIMARY CONSTRAINT NAME",
DF.CONSTRAINT_NAME AS "REFERENCED CONSTRAINT NAME",
DF.OWNER AS "CHILD_TABLE_OWNER",
DF.TABLE_NAME AS "CHILD_TABLE_NAME"
FROM DBA_CONSTRAINTS DC,
(SELECT C.OWNER,
C.CONSTRAINT_NAME,
C.R_CONSTRAINT_NAME,
C.TABLE_NAME
FROM DBA_CONSTRAINTS C
WHERE CONSTRAINT_TYPE = 'R') DF
WHERE DC.CONSTRAINT_NAME = DF.R_CONSTRAINT_NAME
AND DC.OWNER =UPPER('&OWNER'); –查看某个具体的表是否和其它表拥有主外键关系
--查看某个具体的表是否和其它表拥有主外键关系
SELECT DC.OWNER AS "PARENT_TABLE_OWNER",
DC.TABLE_NAME AS "PARENT_TABLE_NAME",
DC.CONSTRAINT_NAME AS "PRIMARY CONSTRAINT NAME",
DF.CONSTRAINT_NAME AS "REFERENCED CONSTRAINT NAME",
DF.OWNER AS "CHILD_TABLE_OWNER",
DF.TABLE_NAME AS "CHILD_TABLE_NAME"
FROM DBA_CONSTRAINTS DC,
(SELECT C.OWNER,
C.CONSTRAINT_NAME,
C.R_CONSTRAINT_NAME,
C.TABLE_NAME
FROM DBA_CONSTRAINTS C
WHERE CONSTRAINT_TYPE = 'R') DF
WHERE DC.CONSTRAINT_NAME = DF.R_CONSTRAINT_NAME
AND DC.OWNER =UPPER('&OWNER')
AND DC.TABLE_NAME=UPPER('&TABLE_NAME');接下来我们要找出在具体的外键字段是否有索引，脚本如下所示：
SELECT CON.OWNER ,
CON.TABLE_NAME,
CON.CONSTRAINT_NAME,
CON.COL_LIST,
'No Indexed' AS INDEX_STATUS
FROM
(SELECT CC.OWNER, CC.TABLE_NAME, CC.CONSTRAINT_NAME,
MAX(DECODE(POSITION, 1, '"' ||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 2,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 3,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 4,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 5,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 6,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 7,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 8,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 9,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 10,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) COL_LIST
FROM DBA_CONSTRAINTS DC, DBA_CONS_COLUMNS CC
WHERE DC.OWNER = CC.OWNER
AND DC.CONSTRAINT_NAME = CC.CONSTRAINT_NAME
AND DC.CONSTRAINT_TYPE = 'R'
AND DC.OWNER NOT IN ('SYS', 'SYSTEM', 'OLAPSYS', 'SYSMAN', 'MDSYS', 'ADMIN')
GROUP BY CC.OWNER, CC.TABLE_NAME, CC.CONSTRAINT_NAME
) CON
WHERE NOT EXISTS (
SELECT 1 FROM
( SELECT TABLE_OWNER, TABLE_NAME,
MAX(DECODE(COLUMN_POSITION, 1, '"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 2,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 3,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 4,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 5,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 6,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 7,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 8,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 9,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 10,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) COL_LIST
FROM DBA_IND_COLUMNS
WHERE TABLE_OWNER NOT IN ('SYS', 'SYSTEM', 'OLAPSYS', 'SYSMAN', 'MDSYS')
GROUP BY TABLE_OWNER, TABLE_NAME, INDEX_NAME ) COL
WHERE CON.OWNER = COL.TABLE_OWNER
AND CON.TABLE_NAME = COL.TABLE_NAME
AND CON.COL_LIST = SUBSTR(COL.COL_LIST, 1, LENGTH(CON.COL_LIST) ) ) ; 如果是ORACLE 11g或以上版本，数据库有分析函数LISTAGG的话，可以使用下面脚本
SELECT CASE
WHEN B.TABLE_NAME IS NULL THEN 'NO INDEXED'
ELSE 'INDEXED'
END AS STATUS,
A.TABLE_OWNER AS TABLE_OWNER,
A.TABLE_NAME AS TABLE_NAME,
A.CONSTRAINT_NAME AS FK_NAME,
A.FK_COLUMNS AS FK_COLUMNS,
B.INDEX_NAME AS INDEX_NAME,
B.INDEX_COLUMNS AS INDEX_COLUMNS
FROM (SELECT A.OWNER AS TABLE_OWNER,
A.TABLE_NAME AS TABLE_NAME,
A.CONSTRAINT_NAME AS CONSTRAINT_NAME,
LISTAGG(A.COLUMN_NAME, ',')
WITHIN GROUP (ORDER BY A.POSITION) FK_COLUMNS
FROM DBA_CONS_COLUMNS A,
DBA_CONSTRAINTS B
WHERE A.CONSTRAINT_NAME = B.CONSTRAINT_NAME
AND B.CONSTRAINT_TYPE = 'R'
AND A.OWNER = B.OWNER
AND A.OWNER NOT IN ( 'SYS', 'SYSTEM', 'OLAPSYS', 'SYSMAN',
'MDSYS' )
GROUP BY A.OWNER,
A.TABLE_NAME,
A.CONSTRAINT_NAME) A,
(SELECT TABLE_OWNER,
TABLE_NAME,
INDEX_NAME,
LISTAGG(C.COLUMN_NAME, ',')
WITHIN GROUP (ORDER BY C.COLUMN_POSITION) INDEX_COLUMNS
FROM DBA_IND_COLUMNS C
GROUP BY TABLE_OWNER,
TABLE_NAME,
INDEX_NAME) B
WHERE A.TABLE_NAME = B.TABLE_NAME(+)
AND A.TABLE_OWNER = B.TABLE_OWNER(+)
AND B.INDEX_COLUMNS(+) LIKE A.FK_COLUMNS
|| '%'
ORDER BY 1 DESC自动生成创建外键索引的脚本
上面的这些脚本已经能找出那些外键字段已经建立或未建立索引，此时如果对外键字段缺少索引的表手工创建索引的话，如果数量很多的话，那么工作量也非常大，下面可以用这个脚本自动生成缺失的索引
/*******************************************************************************************
--脚本功能描述：
-- 对于数据库中外键缺少索引的字段，生成对应的索引（排除一些系统账号，例如sys、system）,如果外键索引超过十个字段
-- 那么这个脚本就不能正确的生成对应的索引，当然也很少有外键设置在超过10个字段的。另外索引表空
-- 空间跟数据表空间相同，如有分开的话，建议在此处再做调整。
********************************************************************************************/
SELECT 'CREATE INDEX ' || OWNER || '.' || REPLACE(CONSTRAINT_NAME,'FK_','IX_') ||
' ON ' || OWNER || '.' || TABLE_NAME || ' (' || COL_LIST ||') TABLESPACE '
|| (SELECT TABLESPACE_NAME FROM DBA_TABLES WHERE OWNER= CON.OWNER AND TABLE_NAME= CON.TABLE_NAME)
AS CREATE_INDEXES_ON_FOREIGN_KEY
FROM
(SELECT CC.OWNER, CC.TABLE_NAME, CC.CONSTRAINT_NAME,
MAX(DECODE(POSITION, 1, '"' ||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 2,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 3,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 4,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 5,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 6,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 7,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 8,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 9,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(POSITION, 10,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) COL_LIST
FROM DBA_CONSTRAINTS DC, DBA_CONS_COLUMNS CC
WHERE DC.OWNER = CC.OWNER
AND DC.CONSTRAINT_NAME = CC.CONSTRAINT_NAME
AND DC.CONSTRAINT_TYPE = 'R'
AND DC.OWNER NOT IN ('SYS', 'SYSTEM', 'OLAPSYS', 'SYSMAN', 'MDSYS', 'ADMIN')
GROUP BY CC.OWNER, CC.TABLE_NAME, CC.CONSTRAINT_NAME
) CON
WHERE NOT EXISTS (
SELECT 1 FROM
( SELECT TABLE_OWNER, TABLE_NAME,
MAX(DECODE(COLUMN_POSITION, 1, '"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 2,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 3,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 4,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 5,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 6,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 7,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 8,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 9,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) ||
MAX(DECODE(COLUMN_POSITION, 10,', '||'"'||
SUBSTR(COLUMN_NAME,1,30) ||'"',NULL)) COL_LIST
FROM DBA_IND_COLUMNS
WHERE TABLE_OWNER NOT IN ('SYS', 'SYSTEM', 'OLAPSYS', 'SYSMAN', 'MDSYS')
GROUP BY TABLE_OWNER, TABLE_NAME, INDEX_NAME ) COL
WHERE CON.OWNER = COL.TABLE_OWNER
AND CON.TABLE_NAME = COL.TABLE_NAME
AND CON.COL_LIST = SUBSTR(COL.COL_LIST, 1, LENGTH(CON.COL_LIST) ) ) ; –脚本使用分析函数LISTAGG， 适用于ORACLE 11g以及以上版本，如果数据库版本是Oracle 11g及以上，就可以使用此脚本替代上面脚本。
SELECT 'CREATE INDEX '
|| OWNER
|| '.'
|| REPLACE(CONSTRAINT_NAME,'FK_','IX_')
|| ' ON '
|| OWNER
|| '.'
|| TABLE_NAME
|| ' ('
|| FK_COLUMNS
||') TABLESPACE '
||
(
SELECT TABLESPACE_NAME
FROM DBA_TABLES
WHERE OWNER= CON.OWNER
AND TABLE_NAME= CON.TABLE_NAME) CREATE_INDEXES_ON_FOREIGN_KEY
FROM (
SELECT CC.OWNER,
CC.TABLE_NAME,
CC.CONSTRAINT_NAME,
LISTAGG(CC.COLUMN_NAME, ',') WITHIN GROUP (ORDER BY CC.POSITION) FK_COLUMNS
FROM DBA_CONS_COLUMNS CC,
DBA_CONSTRAINTS DC
WHERE CC.CONSTRAINT_NAME = DC.CONSTRAINT_NAME
AND DC.CONSTRAINT_TYPE = 'R'
AND CC.OWNER = DC.OWNER
AND DC.OWNER NOT IN ( 'SYS',
'SYSTEM',
'OLAPSYS',
'SYSMAN',
'MDSYS',
'ADMIN' )
GROUP BY CC.OWNER,
CC.TABLE_NAME,
CC.CONSTRAINT_NAME) CON
WHERE NOT EXISTS
(
SELECT 1
FROM (
SELECT TABLE_OWNER,
TABLE_NAME,
INDEX_NAME,
LISTAGG(COLUMN_NAME, ',') WITHIN GROUP (ORDER BY COLUMN_POSITION) FK_COLUMNS
FROM DBA_IND_COLUMNS
WHERE INDEX_OWNER NOT IN ( 'SYS',
'SYSTEM',
'OLAPSYS',
'SYSMAN',
'MDSYS',
'ADMIN' )
GROUP BY TABLE_OWNER,
TABLE_NAME ,INDEX_NAME) COL
WHERE CON.OWNER = COL.TABLE_OWNER
AND CON.TABLE_NAME = COL.TABLE_NAME
AND CON.FK_COLUMNS = SUBSTR(COL.FK_COLUMNS, 1, LENGTH(CON.FK_COLUMNS)) )
ORDER BY 1;参考：http://www.cnblogs.com/kerrycode/p/6723345.html