How to create index on a varchar column that represent date?

Hello there,
I have a column in my table that is a VARCHAR2 and represent a datetime like '2010-08-23 19:00:00' I want to create an index on it and with an specific large like '2010-08-23 19' so i can filter per HOURS.
Any one knows the sentence for this?
Thanx in advance

Vladimir Zakharychev wrote:
I'd highly recommend you heed the advice given: store dates as DATE, numbers as NUMBER, strings as VARCHAR2. I can't imagine any valid reason for storing dates like that (except the undisputable "because I want it that way.") You are likely to see all sorts of inefficiencies with your current design (it will not sort correctly, for example, because it will sort strings, not dates, and the rules for sorting them are different.) The function-based index you created will only work if your query will use that same exact function you created the index on.Not to mention that there is no way the database can enforce the "date" data to actually be a valid date . . . and there will come a time that the application *will not" enforce it ...

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How to create index on a xmltype column stored as CLOB

actually i have two problems.
i uploaded this schemaA.xsd file into xmldb repository without problems. registration also went ok.
BEGIN
DBMS_XMLSCHEMA.registerSchema(
schemaURL => 'http://xmlns.example.com/xdb/documentation/schemaA.xsd'
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,local => TRUE
,genBean => false
,genTypes => TRUE
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END;
then i run this:
create table pf_table_a(
     id VARCHAR2(100) primary key,
     xsd VARCHAR2(3000),
xml_document XMLType
) XMLTYPE COLUMN xml_document
STORE AS CLOB
XMLSCHEMA "http://xmlns.example.com/xdb/documentation/schemaA.xsd"
ELEMENT "order";
and got this error:
SQL> @d:\usr\dev\perftest\create_tables.sql
Table created.
create table pf_table_a(
ERROR at line 1:
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derNo'));
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ERROR at line 1:
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this of course is wrong. because the command is for creating index of a XMLTYPE table. no a column. but what is the correct command? thanks.
jack.

actually i have two problems.
i uploaded this schemaA.xsd file into xmldb repository without problems. registration also went ok.
BEGIN
DBMS_XMLSCHEMA.registerSchema(
schemaURL => 'http://xmlns.example.com/xdb/documentation/schemaA.xsd'
,schemaDoc => sys.UriFactory.getUri('/home/dev/schemaA.xsd')
,local => TRUE
,genBean => false
,genTypes => TRUE
,genTables => false
,enableHierarchy => DBMS_XMLSCHEMA.ENABLE_HIERARCHY_NONE
END;
then i run this:
create table pf_table_a(
     id VARCHAR2(100) primary key,
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xml_document XMLType
) XMLTYPE COLUMN xml_document
STORE AS CLOB
XMLSCHEMA "http://xmlns.example.com/xdb/documentation/schemaA.xsd"
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and got this error:
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Table created.
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ERROR at line 1:
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ERROR at line 1:
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jack.

How to create index on xmltype column

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</Root>
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Ben

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Thanks in advance
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Dear Akshay,
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The database system sometimes does not use a suitable index for a selection, even if there is one. The index used depends on the optimizer used for the database system. You should therefore check if the index you created is also used for the selection (see How to Check if an Index is Used).).
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Leaving content frame.
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''' <returns></returns>
''' <remarks></remarks>
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End If
ctrl = Me.GetNextControl(ctrl, True)
Loop
End Function
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For Each
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Multics
My Serial Port Answer

How to create index on XMLType column extension?

I have an XMLType column named "info" whose corresponding global element has a complexType "InfoType" in namespace "http://example.org/ord". The "InfoType" complexType is extended in two namespaces, "http://example.org/info/zipcode" and "http://example.org/info/street". How do I create a unique index using an "InfoType" element contributed from one of the extension namespaces?
I have included below a SQL script that completely describes the problem.
Thanks in advance for your assistance?
- Ron
BEGIN
DBMS_XMLSCHEMA.registerSchema(
'chapter04prod.xsd',
'<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns="http://example.org/prod"
targetNamespace="http://example.org/prod"
elementFormDefault="unqualified">
<xsd:complexType name="ItemsType">
<xsd:sequence>
<xsd:element name="product" type="ProductType"/>
</xsd:sequence>
</xsd:complexType>
<xsd:complexType name="ProductType">
<xsd:sequence>
<xsd:element name="number" type="xsd:integer"/>
<xsd:element name="name" type="xsd:string"/>
<xsd:element name="size" type="SizeType"/>
<xsd:element name="color" type="ColorType"/>
</xsd:sequence>
</xsd:complexType>
<xsd:complexType name="SizeType">
<xsd:simpleContent>
<xsd:extension base="xsd:integer">
<xsd:attribute name="system" type="xsd:string"/>
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
<xsd:complexType name="ColorType">
<xsd:attribute name="value" type="xsd:string"/>
</xsd:complexType>
</xsd:schema>',
TRUE,
TRUE,
FALSE,
FALSE);
END;
BEGIN
DBMS_XMLSCHEMA.registerSchema(
'chapter04ord1.xsd',
'<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://example.org/ord"
xmlns="http://example.org/ord"
xmlns:prod="http://example.org/prod"
elementFormDefault="qualified">
<xsd:import namespace="http://example.org/prod"
schemaLocation="chapter04prod.xsd"/>
<xsd:simpleType name="OrderNumType">
<xsd:restriction base="xsd:string"/>
</xsd:simpleType>
<xsd:complexType name="InfoType"/>
<xsd:complexType name="CustomerType">
<xsd:all>
<xsd:element name="name" type="CustNameType"/>
<xsd:element name="number" type="xsd:integer"/>
<xsd:element name="info" type="InfoType" form="unqualified"/>
</xsd:all>
</xsd:complexType>
<xsd:simpleType name="CustNameType">
<xsd:restriction base="xsd:string"/>
</xsd:simpleType>
<xsd:element name="order" type="OrderType"/>
<xsd:element name="customer" type="CustomerType"/>
<xsd:complexType name="OrderType">
<xsd:sequence>
<xsd:element name="number" type="OrderNumType"/>
<xsd:element name="customer" type="CustomerType"
maxOccurs="unbounded"/>
<xsd:element name="items" type="prod:ItemsType"/>
</xsd:sequence>
</xsd:complexType>
</xsd:schema>',
TRUE,
TRUE,
FALSE,
FALSE);
END;
BEGIN
DBMS_XMLSCHEMA.registerSchema(
'chapter04infozipcode.xsd',
'<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:ord="http://example.org/ord"
xmlns="http://example.org/info/zipcode"
targetNamespace="http://example.org/info/zipcode"
elementFormDefault="unqualified">
<xsd:import namespace="http://example.org/ord"
schemaLocation="chapter04ord1.xsd"/>
<xsd:complexType name="InfoType">
<xsd:complexContent>
<xsd:extension base="ord:InfoType">
<xsd:sequence>
<xsd:element name="zipcode" type="xsd:string"/>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
</xsd:schema>',
TRUE,
TRUE,
FALSE,
FALSE);
END;
BEGIN
DBMS_XMLSCHEMA.registerSchema(
'chapter04infostreet.xsd',
'<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:ord="http://example.org/ord"
xmlns="http://example.org/info/street"
targetNamespace="http://example.org/info/street"
elementFormDefault="unqualified">
<xsd:import namespace="http://example.org/ord"
schemaLocation="chapter04ord1.xsd"/>
<xsd:complexType name="InfoType">
<xsd:complexContent>
<xsd:extension base="ord:InfoType">
<xsd:sequence>
<xsd:element name="street" type="xsd:string"/>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
</xsd:schema>',
TRUE,
TRUE,
FALSE,
FALSE);
END;
BEGIN
DBMS_XMLSCHEMA.registerSchema(
'chapter04nonamespace.xsd',
'<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:ord="http://example.org/ord">
<xsd:import namespace="http://example.org/ord"
schemaLocation="chapter04ord1.xsd"/>
<xsd:element name="info" type="ord:InfoType">
</xsd:schema>',
TRUE,
TRUE,
FALSE,
FALSE);
END;
CREATE TABLE customer (
name VARCHAR(64),
number INTEGER,
info XMLTYPE)
XMLType info STORE AS OBJECT RELATIONAL
XMLSCHEMA "chapter04nonamespace.xsd"
ELEMENT "info";
INSERT INTO customer (name, number, info)
VALUES ('George Jones', 1,
XMLType(
'<info xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:street="http://example.org/info/zipcode"
xsi:type="zipcode:InfoType">
<zipcode>28877</zipcode>
</info>');
INSERT INTO customer (name, number, info)
VALUES ('Jim Jones', 2,
XMLType(
'<info xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:street="http://example.org/info/street"
xsi:type="street:InfoType">
<street>3456 Autumn Lane</street>
</info>');
SELECT name,
extractValue(info, '/info/street')
FROM customer
WHERE extractValue(info, '/info/street/text()') LIKE '3456%';
-- How does one create a unique index as follows?
CREATE UNIQUE INDEX customer_infostreet ON customer (??????);
-- The following insert should fail with unique index violation!
INSERT INTO customer (name, number, info)
VALUES ('Jerry Jones', 3,
XMLType(
'<info xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:street="http://example.org/info/street"
xsi:type="street:InfoType">
<street>3456 Autumn Lane</street>
</info>');

Ron
Glad you found a solution.. However a more efficient solution is show below
SQL> connect sys/ as sysdba
Enter password:
Connected.
SQL> set define on
SQL> --
SQL> define USERNAME = OTNTEST
SQL> --
SQL> def PASSWORD = OTNTEST
SQL> --
SQL> def USER_TABLESPACE = USERS
SQL> --
SQL> def TEMP_TABLESPACE = TEMP
SQL> --
SQL> drop user &USERNAME cascade
2 /
old   1: drop user &USERNAME cascade
new   1: drop user OTNTEST cascade
User dropped.
SQL> grant connect, resource to &USERNAME identified by &PASSWORD
2 /
old   1: grant connect, resource to &USERNAME identified by &PASSWORD
new   1: grant connect, resource to OTNTEST identified by OTNTEST
Grant succeeded.
SQL> grant create any directory, drop any directory to &USERNAME
2 /
old   1: grant create any directory, drop any directory to &USERNAME
new   1: grant create any directory, drop any directory to OTNTEST
Grant succeeded.
SQL> grant alter session, create view to &USERNAME
2 /
old   1: grant alter session, create view to &USERNAME
new   1: grant alter session, create view to OTNTEST
Grant succeeded.
SQL> alter user &USERNAME default tablespace &USER_TABLESPACE temporary tablespace &TEMP_TABLESPACE
2 /
old   1: alter user &USERNAME default tablespace &USER_TABLESPACE temporary tablespace &TEMP_TABLESPACE
new   1: alter user OTNTEST default tablespace USERS temporary tablespace TEMP
User altered.
SQL> connect &USERNAME/&PASSWORD
Connected.
SQL> --
SQL> alter session set events ='19027 trace name context forever, level 0x800'
2 /
Session altered.
SQL> BEGIN
2 DBMS_XMLSCHEMA.registerSchema(
3 'chapter04prod.xsd',
4 '<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://example.org/prod" targetNamespa
fault="unqualified">
5     <xsd:complexType name="ItemsType">
6             <xsd:sequence>
7                     <xsd:element name="product" type="ProductType"/>
8             </xsd:sequence>
9     </xsd:complexType>
10     <xsd:complexType name="ProductType">
11             <xsd:sequence>
12                     <xsd:element name="num" type="xsd:integer"/>
13                     <xsd:element name="name" type="xsd:string"/>
14                     <xsd:element name="size" type="SizeType"/>
15                     <xsd:element name="color" type="ColorType"/>
16             </xsd:sequence>
17     </xsd:complexType>
18     <xsd:complexType name="SizeType">
19             <xsd:simpleContent>
20                     <xsd:extension base="xsd:integer">
21                             <xsd:attribute name="system" type="xsd:string"/>
22                     </xsd:extension>
23             </xsd:simpleContent>
24     </xsd:complexType>
25     <xsd:complexType name="ColorType">
26             <xsd:attribute name="value" type="xsd:string"/>
27     </xsd:complexType>
28 </xsd:schema>',
29 TRUE, TRUE, FALSE, FALSE);
30 END;
31 /
PL/SQL procedure successfully completed.
SQL> BEGIN
2 DBMS_XMLSCHEMA.registerSchema(
3 'chapter04ord1.xsd',
4 '<xsd:schema xmlns:xdb="http://xmlns.oracle.com/xdb" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns
://example.org/prod" targetNamespace="http://example.org/ord" elementFormDefault="qualified">
5     <xsd:import namespace="http://example.org/prod" schemaLocation="chapter04prod.xsd"/>
6     <xsd:simpleType name="OrderNumType">
7             <xsd:restriction base="xsd:string"/>
8     </xsd:simpleType>
9     <xsd:complexType name="InfoType" xdb:SQLType="INFO_TYPE_T"/>
10     <xsd:complexType name="CustomerType">
11             <xsd:all>
12                     <xsd:element name="name" type="CustNameType"/>
13                     <xsd:element name="num" type="xsd:integer"/>
14                     <xsd:element name="info" type="InfoType" minOccurs="1" form="unqualified"/>
15             </xsd:all>
16     </xsd:complexType>
17     <xsd:simpleType name="CustNameType">
18             <xsd:restriction base="xsd:string"/>
19     </xsd:simpleType>
20     <xsd:element name="customers" type="CustomersType"/>
21     <xsd:complexType name="CustomersType">
22             <xsd:sequence>
23                     <xsd:element name="customer" type="CustomerType" minOccurs="0" maxOccurs="unbounded"
24             </xsd:sequence>
25     </xsd:complexType>
26     <xsd:element name="order" type="OrderType"/>
27     <xsd:element name="customer" type="CustomerType"/>
28     <xsd:complexType name="OrderType">
29             <xsd:sequence>
30                     <xsd:element name="num" type="OrderNumType"/>
31                     <xsd:element name="customer" type="CustomerType" maxOccurs="unbounded"/>
32                     <xsd:element name="items" type="prod:ItemsType"/>
33             </xsd:sequence>
34     </xsd:complexType>
35 </xsd:schema>',
36 TRUE, TRUE, FALSE, FALSE);
37 END;
38 /
PL/SQL procedure successfully completed.
SQL> BEGIN
2 DBMS_XMLSCHEMA.registerSchema(
3 'chapter04infozipcode.xsd',
4 '<xsd:schema xmlns:xdb="http://xmlns.oracle.com/xdb" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns
//example.org/info/zipcode" targetNamespace="http://example.org/info/zipcode" elementFormDefault="unqualifie
5     <xsd:import namespace="http://example.org/ord" schemaLocation="chapter04ord1.xsd"/>
6     <xsd:complexType name="InfoType" xdb:SQLType="ZIPCODE_INFO_TYPE_T">
7             <xsd:complexContent>
8                     <xsd:extension base="ord:InfoType">
9                             <xsd:sequence>
10                                     <xsd:element name="zipcode" type="xsd:string"/>
11                                     <xsd:element name="suffix" type="xsd:string"/>
12                             </xsd:sequence>
13                     </xsd:extension>
14             </xsd:complexContent>
15     </xsd:complexType>
16 </xsd:schema>',
17 TRUE, TRUE, FALSE, FALSE);
18 END;
19 /
PL/SQL procedure successfully completed.
SQL>
SQL> BEGIN
2 DBMS_XMLSCHEMA.registerSchema(
3 'chapter04infostreet.xsd',
4 '<xsd:schema xmlns:xdb="http://xmlns.oracle.com/xdb" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns
//example.org/info/street" targetNamespace="http://example.org/info/street" elementFormDefault="unqualified"
5     <xsd:import namespace="http://example.org/ord" schemaLocation="chapter04ord1.xsd"/>
6     <xsd:complexType name="InfoType" xdb:SQLType="STREET_INFO_TYPE_T">
7             <xsd:complexContent>
8                     <xsd:extension base="ord:InfoType">
9                             <xsd:sequence>
10                                     <xsd:element name="street" type="xsd:string"/>
11                                     <xsd:element name="suffix" type="xsd:string"/>
12                             </xsd:sequence>
13                     </xsd:extension>
14             </xsd:complexContent>
15     </xsd:complexType>
16 </xsd:schema>',
17 TRUE, TRUE, FALSE, FALSE);
18 END;
19 /
PL/SQL procedure successfully completed.
SQL>
SQL> BEGIN
2 DBMS_XMLSCHEMA.registerSchema(
3 'chapter04nonamespace.xsd',
4 '<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:ord="http://example.org/ord">
5     <xsd:import namespace="http://example.org/ord" schemaLocation="chapter04ord1.xsd"/>
6     <xsd:element name="info" type="ord:InfoType"/>
7 </xsd:schema>',
8 TRUE, TRUE, FALSE, FALSE);
9 END;
10 /
PL/SQL procedure successfully completed.
SQL>
SQL> CREATE TABLE customer (
2 name VARCHAR(64),
3 num INTEGER,
4 info XMLTYPE)
5 XMLType info STORE AS OBJECT RELATIONAL
6 XMLSCHEMA "chapter04nonamespace.xsd"
7 ELEMENT "info";
Table created.
SQL>
SQL> INSERT INTO customer (name, num, info)
2 VALUES ('George Jones', 1,
3 XMLType(
4 '<info xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:zipcode="http://example.org/info/zip
5     <zipcode>28877</zipcode>
6     <suffix>s1</suffix>
7 </info>'));
1 row created.
SQL>
SQL> INSERT INTO customer (name, num, info)
2 VALUES ('Jim Jones', 2,
3 XMLType(
4 '<info xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:street="http://example.org/info/stre
5     <street>3456 Autumn Lane</street>
6     <suffix>s2</suffix>
7 </info>'));
1 row created.
SQL> /
1 row created.
SQL> SELECT name,
2         extractValue(info, '/info/zipcode'),
3         extractValue(info, '/info/street')
4    FROM customer
5 WHERE extractValue(info, '/info/zipcode/text()') LIKE '2%'
6     OR extractValue(info, '/info/street/text()') LIKE '3456%';
NAME
EXTRACTVALUE(INFO,'/INFO/ZIPCODE')
EXTRACTVALUE(INFO,'/INFO/STREET')
George Jones
28877
Jim Jones
3456 Autumn Lane
NAME
EXTRACTVALUE(INFO,'/INFO/ZIPCODE')
EXTRACTVALUE(INFO,'/INFO/STREET')
Jim Jones
3456 Autumn Lane
SQL>
SQL> CREATE UNIQUE INDEX customer_infozipcode ON customer(
2 extractValue
3 (
4    info,
5    '/info[@xsi:type="zipcode:InfoType"]/zipcode',
6    'xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
7    xmlns:zipcode="http://example.org/info/zipcode"'
8 ))
9 /
Index created.
SQL> select column_name
2    from user_ind_columns
3   where INDEX_NAME = 'CUSTOMER_INFOZIPCODE'
4 /
COLUMN_NAME
SYS_NC00014$
SQL> select INDEX_NAME,COLUMN_EXPRESSION
2    from user_ind_expressions
3 /
INDEX_NAME
COLUMN_EXPRESSION
CUSTOMER_INFOZIPCODE
EXTRACTVALUE(SYS_MAKEXML('0341F05603124922B4F6F94DC5E30C2F',4870,"SYS_NC00004$",
SQL> DROP INDEX CUSTOMER_INFOZIPCODE
2 /
Index dropped.
SQL> desc INFO_TYPE_T
INFO_TYPE_T is NOT FINAL
Name                                      Null?    Type
SYS_XDBPD$                                         XDB.XDB$RAW_LIST_T
SQL> --
SQL> desc ZIPCODE_INFO_TYPE_T
ZIPCODE_INFO_TYPE_T extends OTNTEST.INFO_TYPE_T
ZIPCODE_INFO_TYPE_T is NOT FINAL
Name                                      Null?    Type
SYS_XDBPD$                                         XDB.XDB$RAW_LIST_T
zipcode                                            VARCHAR2(4000 CHAR)
suffix                                             VARCHAR2(4000 CHAR)
SQL> --
SQL> desc STREET_INFO_TYPE_T
STREET_INFO_TYPE_T extends OTNTEST.INFO_TYPE_T
STREET_INFO_TYPE_T is NOT FINAL
Name                                      Null?    Type
SYS_XDBPD$                                         XDB.XDB$RAW_LIST_T
street                                             VARCHAR2(4000 CHAR)
suffix                                             VARCHAR2(4000 CHAR)
SQL> --
SQL> CREATE UNIQUE INDEX customer_infozipcode ON customer(TREAT(INFO.XMLDATA AS ZIPCODE_INFO_TYPE_T)."zipcod
2 /
Index created.
SQL> select column_name
2    from user_ind_columns
3   where INDEX_NAME = 'CUSTOMER_INFOZIPCODE'
4 /
COLUMN_NAME
TREAT("SYS_NC00007$" AS "ZIPCODE_INFO_TYPE_T")."zipcode"
SQL> select INDEX_NAME,COLUMN_EXPRESSION
2    from user_ind_expressions
3 /
no rows selected
SQL> INSERT INTO customer (name, num, info)
2 VALUES ('Jerry Jones', 3,
3 XMLType(
4 '<info xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:zipcode="http://example.org/info/zip
5     <zipcode>28877</zipcode>
6     <suffix>s1</suffix>
7 </info>'))
8 /
INSERT INTO customer (name, num, info)
ERROR at line 1:
ORA-00001: unique constraint (OTNTEST.CUSTOMER_INFOZIPCODE) violated
SQL> INSERT INTO customer (name, num, info)
2 VALUES ('Jerry Jones', 3,
3 XMLType(
4 '<info xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:street="http://example.org/info/stre
5     <street>3456 Autumn Lane</street>
6     <suffix>s3</suffix>
7 </info>'))
8 /
1 row created.
SQL>In you solution a functional index was created. In my case, by breaking the XML abstraction, and using object-relational SQL to create the index (DDL statements are the one case where I feel this is acceptable) I was able to create a pure B-TREE index which has the same effect..

How to create index for a column of a view

Hi,
I have created view for a table and then i am trying to create index for a column of that view. i am using the query "CREATE INDEX index_name ON view_name (col)". but Mysql is showing error like "view_name is not a base table".
How can i do that......

As mentioned this is a java forum not a mysql forum, but as I know the answer - you can't create an index directly on a view in mysql.

How to create index on xmtype column

Hi,
I have a table as follows
CREATE TABLE T_TEST_XML (PROCESS_ID NUMBER, TXT_XML XMLTYPE);
I query the above table very frequently with the query
SELECT * FROM T_TEST_XML TXS WHERE EXISTSNODE(TXS.TXT_XML, '/order[status="PEN"]') = 1
How to create function based index on the TXT_XML column for the xpath expression /order[status="PEN"]' to improve the query performance?
Thank you

Actually if you are limited to using older software
1. Consider defining an XML Schema and storing the XML using object relational storage.
or
2. If you must store the XML as CLOB create the index on extractValue(), rather than existsNode() and supply the predicate value at the SQL level rather than the XPATH level.
SQL> DROP TABLE T_TEST_XML
2 /
Table dropped.
SQL> CREATE TABLE T_TEST_XML (PROCESS_ID NUMBER, TXT_XML XMLTYPE)
2 /
Table created.
SQL> create INDEX T_TEXT_XML_IDX on T_TEST_XML( extractValue(TXT_XML,'/order/status'))
2 /
Index created.
SQL> set autotrace on explain
SQL> --
SQL> SELECT *
2    FROM T_TEST_XML TXS
3   WHERE ExistsNode(TXT_XML,'/order[status="PEN"]') = 1
4 /
no rows selected
Execution Plan
Plan hash value: 3001212210
| Id | Operation          | Name       | Rows | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT   |            |     1 | 2017 |    31   (0)| 00:00:01 |
|   1 | NESTED LOOPS SEMI |            |     1 | 2017 |    31   (0)| 00:00:01 |
|   2 |   TABLE ACCESS FULL| T_TEST_XML |     1 | 2015 |     2   (0)| 00:00:01 |
|* 3 |   XPATH EVALUATION |            |       |       |            |          |
Predicate Information (identified by operation id):
   3 - filter("P"."C_01$"='PEN')
Note
   - dynamic sampling used for this statement (level=2)
SQL> SELECT *
2    FROM T_TEST_XML TXS
3   WHERE extractValue(TXT_XML,'/order/status') = 'PEN'
4 /
no rows selected
Execution Plan
Plan hash value: 1430727070
| Id | Operation                   | Name           | Rows | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT            |                |     1 | 2015 |     1   (0)| 00:00:01 |
|   1 | TABLE ACCESS BY INDEX ROWID| T_TEST_XML     |     1 | 2015 |     1   (0)| 00:00:01 |
|* 2 |   INDEX RANGE SCAN          | T_TEXT_XML_IDX |     1 |       |     1   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - access(EXTRACTVALUE(SYS_MAKEXML(0,"SYS_NC00003$"),'/order/status',null,0,0,5242
              93,133120)='PEN')
Note
   - dynamic sampling used for this statement (level=2)
SQL>
SQL>
SQL>
SQL>
SQL>
SQL>This allows the index to support querying on any value of status, rather than just PEN

How to create index on XMLTYPE ordered collection table?

I am using Oracle 11.2.0.2.
Essentially, my XML documents have a 3-level hierarchy:
event
+---action [1:n]
         +---- param   [1:n]
I am trying to create indexes on ordered collection tables, but can not get the syntax right...
I have created a table with an object-relational XMLType column:
CREATE TABLE T_C_RMP_MNTRNG_XML_FULL_IL4 (
MESSAGE_ID NUMBER(22,0) NOT NULL ENABLE,
XML_EVAL_ID NUMBER(22,0),
VIN7 VARCHAR2(7 BYTE),
FLEET_ID VARCHAR2(50 BYTE),
CSC_SW_VERSION VARCHAR2(100 BYTE),
RECEIVED DATE,
XML_CONTENT SYS.XMLTYPE ,
DWH_LM_TS_UTC DATE NOT NULL ENABLE,
CONSTRAINT PK_C_RMP_MNTRNG_XML_FULL_IL4 PRIMARY KEY (MESSAGE_ID)
) NOLOGGING TABLESPACE CATALOG
VARRAY "XML_CONTENT"."XMLDATA"."action" STORE AS TABLE "T_OR_MON_ACTION" (
NOLOGGING TABLESPACE "CATALOG"
VARRAY "param" STORE AS TABLE "T_OR_MON_ACTION_PARAM" (
NOLOGGING TABLESPACE "CATALOG"
) RETURN AS LOCATOR
) RETURN AS LOCATOR
XMLTYPE XML_CONTENT STORE AS OBJECT RELATIONAL XMLSCHEMA "http://mydomain.com/cs.xsd" ELEMENT "monitoring";
I am running the following SELECT:
SELECT EVENT_ID, ACTION_SUB_ID, MESSAGE_ID, ACTION_TYPE, UNIXTS_TO_DATE(ACTION_TIMESTAMP) ACTION_TIMESTAMP
FROM T_C_RMP_MNTRNG_XML_FULL_IL4,
XMLTABLE(
'for $i1 in /monitoring ,
$i2 in $i1/action
return element r {
$i1/eventId,
$i2
PASSING XML_CONTENT COLUMNS
EVENT_ID VARCHAR(40) PATH 'eventId',
ACTION_SUB_ID INTEGER PATH 'action/actionSubId',
ACTION_TYPE VARCHAR2(100) PATH 'action/type',
ACTION_TIMESTAMP NUMBER(13,0) PATH 'action/time'
) T2
WHERE (
EVENT_ID IS NOT NULL AND ACTION_SUB_ID IS NOT NULL
The explain plan looks like this (sorry, don't know how to get this formatted any "eye-friendlier"):
| Id | Operation          | Name                        | Rows | Bytes |TempSpc| Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT   |                             | 1609K| 6316M|       | 6110K (1)| 20:22:11 |
|* 1 | HASH JOIN         |                             | 1609K| 6316M|   111M| 6110K (1)| 20:22:11 |
|   2 |   TABLE ACCESS FULL| T_C_RMP_MNTRNG_XML_FULL_IL4 |   582K|   104M|       | 5241   (1)| 00:01:03 |
|* 3 |   TABLE ACCESS FULL| T_OR_MON_ACTION             |    32M|   117G|       |   105K (2)| 00:21:08 |
Predicate Information (identified by operation id):
   1 - access("NESTED_TABLE_ID"="T_C_RMP_MNTRNG_XML_FULL_IL4"."SYS_NC0001300014$")
       filter(CAST(SYS_XQ_UPKXML2SQL(SYS_XQEXVAL(SYS_XQEXTRACT(XMLCONCAT(SYS_XMLGEN("T_C_RMP_MNTRN
              G_XML_FULL_IL4"."SYS_NC00017$",NULL,SYS_XMLCONV("T_C_RMP_MNTRNG_XML_FULL_IL4"."SYS_NC00012$",0,32,
              'EC1EEF23FD023A27E04032A06D930A8D',3,3783,1)),SYS_MAKEXML('EC1EEF23FD023A27E04032A06D930A8D',3780,
              "T_C_RMP_MNTRNG_XML_FULL_IL4"."SYS_NC00008$","SYS_ALIAS_0"."SYS_NC_ROWINFO$")),'/eventId',NULL),0,
              0,20971520,0),50,1,2) AS VARCHAR(40) ) IS NOT NULL)
   3 - filter(CAST(TO_NUMBER(TO_CHAR("SYS_ALIAS_0"."actionSubId")) AS INTEGER ) IS NOT NULL)
Note
   - dynamic sampling used for this statement (level=2)
   - Unoptimized XML construct detected (enable XMLOptimizationCheck for more information)
The XML schema looks like this:
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" xmlns:oraxdb="http://xmlns.oracle.com/xdb" oraxdb:storeVarrayAsTable="true" oraxdb:flags="2105639" oraxdb:schemaURL="http://mydomain.com/cs.xsd" oraxdb:schemaOwner="MYUSER" oraxdb:numProps="23">
<xs:element name="monitoring" oraxdb:propNumber="3785" oraxdb:global="true" oraxdb:SQLName="monitoring" oraxdb:SQLType="monitoring755_T" oraxdb:SQLSchema="MYUSER" oraxdb:memType="258" oraxdb:defaultTable="monitoring757_TAB" oraxdb:defaultTableSchema="MYUSER">
    <xs:complexType oraxdb:SQLType="monitoring755_T" oraxdb:SQLSchema="MYUSER">
      <xs:sequence>
        <xs:element maxOccurs="unbounded" ref="action" oraxdb:propNumber="3780" oraxdb:global="false" oraxdb:SQLName="action" oraxdb:SQLType="action752_T" oraxdb:SQLSchema="MYUSER" oraxdb:memType="258" oraxdb:MemInline="false" oraxdb:SQLInline="true" oraxdb:JavaInline="false" oraxdb:SQLCollType="action756_COLL" oraxdb:SQLCollSchema="MYUSER"/>
        <xs:element ref="reservationType" oraxdb:propNumber="3781" oraxdb:global="false" oraxdb:SQLName="reservationType" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:MemInline="false" oraxdb:SQLInline="true" oraxdb:JavaInline="false"/>
        <xs:element ref="softwareVersion" oraxdb:propNumber="3782" oraxdb:global="false" oraxdb:SQLName="softwareVersion" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:MemInline="false" oraxdb:SQLInline="true" oraxdb:JavaInline="false"/>
        <xs:element ref="eventId" oraxdb:propNumber="3783" oraxdb:global="false" oraxdb:SQLName="eventId" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:MemInline="false" oraxdb:SQLInline="true" oraxdb:JavaInline="false"/>
        <xs:element ref="vin" oraxdb:propNumber="3784" oraxdb:global="false" oraxdb:SQLName="vin" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:MemInline="false" oraxdb:SQLInline="true" oraxdb:JavaInline="false"/>
      </xs:sequence>
    </xs:complexType>
</xs:element>
<xs:element name="action" oraxdb:propNumber="3790" oraxdb:global="true" oraxdb:SQLName="action" oraxdb:SQLType="action752_T" oraxdb:SQLSchema="MYUSER" oraxdb:memType="258" oraxdb:defaultTable="action754_TAB" oraxdb:defaultTableSchema="MYUSER">
    <xs:complexType oraxdb:SQLType="action752_T" oraxdb:SQLSchema="MYUSER">
      <xs:sequence>
        <xs:element ref="type" oraxdb:propNumber="3786" oraxdb:global="false" oraxdb:SQLName="type" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:MemInline="false" oraxdb:SQLInline="true" oraxdb:JavaInline="false"/>
        <xs:element maxOccurs="unbounded" ref="param" oraxdb:propNumber="3787" oraxdb:global="false" oraxdb:SQLName="param" oraxdb:SQLType="param749_T" oraxdb:SQLSchema="MYUSER" oraxdb:memType="258" oraxdb:MemInline="false" oraxdb:SQLInline="true" oraxdb:JavaInline="false" oraxdb:SQLCollType="param753_COLL" oraxdb:SQLCollSchema="MYUSER"/>
        <xs:element ref="actionSubId" oraxdb:propNumber="3788" oraxdb:global="false" oraxdb:SQLName="actionSubId" oraxdb:SQLType="NUMBER" oraxdb:memType="2" oraxdb:MemInline="false" oraxdb:SQLInline="true" oraxdb:JavaInline="false"/>
        <xs:element ref="time" oraxdb:propNumber="3789" oraxdb:global="false" oraxdb:SQLName="time" oraxdb:SQLType="NUMBER" oraxdb:memType="2" oraxdb:MemInline="false" oraxdb:SQLInline="true" oraxdb:JavaInline="false"/>
      </xs:sequence>
    </xs:complexType>
</xs:element>
<xs:element name="type" type="xs:string" oraxdb:propNumber="3791" oraxdb:global="true" oraxdb:SQLName="type" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:defaultTable="type751_TAB" oraxdb:defaultTableSchema="MYUSER"/>
<xs:element name="param" oraxdb:propNumber="3794" oraxdb:global="true" oraxdb:SQLName="param" oraxdb:SQLType="param749_T" oraxdb:SQLSchema="MYUSER" oraxdb:memType="258" oraxdb:defaultTable="param750_TAB" oraxdb:defaultTableSchema="MYUSER">
    <xs:complexType oraxdb:SQLType="param749_T" oraxdb:SQLSchema="MYUSER">
      <xs:sequence>
        <xs:element minOccurs="0" ref="value" oraxdb:propNumber="3792" oraxdb:global="false" oraxdb:SQLName="value" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:MemInline="false" oraxdb:SQLInline="true" oraxdb:JavaInline="false"/>
        <xs:element ref="key" oraxdb:propNumber="3793" oraxdb:global="false" oraxdb:SQLName="key" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:MemInline="false" oraxdb:SQLInline="true" oraxdb:JavaInline="false"/>
      </xs:sequence>
    </xs:complexType>
</xs:element>
<xs:element name="value" type="xs:string" oraxdb:propNumber="3795" oraxdb:global="true" oraxdb:SQLName="value" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:defaultTable="value748_TAB" oraxdb:defaultTableSchema="MYUSER"/>
<xs:element name="key" type="xs:string" oraxdb:propNumber="3796" oraxdb:global="true" oraxdb:SQLName="key" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:defaultTable="key747_TAB" oraxdb:defaultTableSchema="MYUSER"/>
<xs:element name="actionSubId" type="xs:integer" oraxdb:propNumber="3797" oraxdb:global="true" oraxdb:SQLName="actionSubId" oraxdb:SQLType="NUMBER" oraxdb:memType="2" oraxdb:defaultTable="actionSubId746_TAB" oraxdb:defaultTableSchema="MYUSER"/>
<xs:element name="time" type="xs:integer" oraxdb:propNumber="3798" oraxdb:global="true" oraxdb:SQLName="time" oraxdb:SQLType="NUMBER" oraxdb:memType="2" oraxdb:defaultTable="time745_TAB" oraxdb:defaultTableSchema="MYUSER"/>
<xs:element name="reservationType" type="xs:string" oraxdb:propNumber="3799" oraxdb:global="true" oraxdb:SQLName="reservationType" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:defaultTable="reservationType744_TAB" oraxdb:defaultTableSchema="MYUSER"/>
<xs:element name="softwareVersion" type="xs:string" oraxdb:propNumber="3800" oraxdb:global="true" oraxdb:SQLName="softwareVersion" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:defaultTable="softwareVersion743_TAB" oraxdb:defaultTableSchema="MYUSER"/>
<xs:element name="eventId" type="xs:string" oraxdb:propNumber="3801" oraxdb:global="true" oraxdb:SQLName="eventId" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:defaultTable="eventId742_TAB" oraxdb:defaultTableSchema="MYUSER"/>
<xs:element name="vin" type="xs:string" oraxdb:propNumber="3802" oraxdb:global="true" oraxdb:SQLName="vin" oraxdb:SQLType="VARCHAR2" oraxdb:memType="1" oraxdb:defaultTable="vin741_TAB" oraxdb:defaultTableSchema="MYUSER"/>
</xs:schema>
How can I create an index on these ordered collection tables in order to improve performance?
I found the example at http://docs.oracle.com/cd/E11882_01/appdev.112/e23094/xdb_rewrite.htm#ADXDB5859 but am not able to apply it to this particular case...
Thank you in advance...

If the schema is not annotated then xs:integer and xs:string are mapped to NUMBER and VARCHAR2(4000) datatypes, so you have to use those in your query in order to avoid unnecessary typecasting operations.
You should also use chained XMLTABLEs when accessing a parent/child relationship instead of a FLWOR expression, otherwise the CBO may not rewrite the XQuery correctly (maybe it's fixed in the latest release).
If you make those changes, the plan should show cleaner predicates :
SQL> SELECT EVENT_ID, ACTION_SUB_ID, MESSAGE_ID, ACTION_TYPE, ACTION_TIMESTAMP
2 FROM test_table,
3 XMLTABLE('/monitoring'
4    PASSING XML_CONTENT COLUMNS
5      EVENT_ID         VARCHAR2(4000) PATH 'eventId',
6      actions          XMLTYPE        PATH 'action'
7    ) T1,
8 XMLTABLE('/action'
9    PASSING actions COLUMNS
10      ACTION_SUB_ID    NUMBER PATH 'actionSubId',
11      ACTION_TYPE      VARCHAR2(4000) PATH 'type',
12      ACTION_TIMESTAMP NUMBER PATH 'time'
13 ) T2
14 WHERE EVENT_ID IS NOT NULL
15 AND ACTION_SUB_ID IS NOT NULL
16 ;
Execution Plan
Plan hash value: 1763884463
| Id | Operation                    | Name            | Rows | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT             |                 |   109 |   220K|     6 (17)| 00:00:01 |
|   1 | MERGE JOIN                  |                 |   109 |   220K|     6 (17)| 00:00:01 |
|* 2 |   TABLE ACCESS BY INDEX ROWID| TEST_TABLE      |    11 |   352 |     2   (0)| 00:00:01 |
|   3 |    INDEX FULL SCAN           | SYS_C007567     |    11 |       |     1   (0)| 00:00:01 |
|* 4 |   SORT JOIN                  |                 |   109 |   216K|     4 (25)| 00:00:01 |
|* 5 |    TABLE ACCESS FULL         | T_OR_MON_ACTION |   109 |   216K|     3   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - filter("TEST_TABLE"."SYS_NC00012$" IS NOT NULL)
   4 - access("SYS_ALIAS_0"."NESTED_TABLE_ID"="TEST_TABLE"."SYS_NC0000800009$")
       filter("SYS_ALIAS_0"."NESTED_TABLE_ID"="TEST_TABLE"."SYS_NC0000800009$")
   5 - filter("SYS_ALIAS_0"."actionSubId" IS NOT NULL)
Note
   - dynamic sampling used for this statement (level=2)
Now, if still necessary, it all boils down to choosing a technique to index NULL values :
- composite index with a not null or constant column
- FBI
- bitmap
Pick one that best fits your data, selectivity and activity on the tables.

How to create index on a single parition

Hi,
I have a table which has got 7 partitons,I want to index only one partition how do it?
i am using oracle 11g.Also i want to know if it is possible to create an index within a o partiotn only fr some values..
Edited by: user8731258 on Jul 13, 2012 12:35 AM

Hi,
I've been thinking a bit about your requirement.
One way could be to use the fact that index do not "store" nulls.
Let's make a table with data :SQL> create table t
2 (
3 grp integer,
4 id integer,
5 val varchar2(10)
6 )
7 partition by range(grp)
8 (
9 partition p01 values less than (2)
10 ,partition p02 values less than (3)
11 ,partition p03 values less than (4)
12 ,partition pXX values less than (maxvalue)
13 );
Table created.
SQL> insert into t select 1+mod(level,4), level, dbms_random.string('a',10) from dual connect by level <= 200000;
200000 rows created.
SQL> select grp, count(*) cnt from t group by grp order by grp;
       GRP       CNT
      1     50000
      2     50000
      3     50000
      4     50000
SQL> select grp, count(*) cnt from t group by grp order by grp;
       GRP       CNT
      1     50000
      2     50000
      3     50000
      4     50000
SQL> begin
2 dbms_stats.gather_table_stats(
3 ownname => user,
4 tabname => 'T',
5 method_opt => 'for all columns size 1',
6 granularity => 'global and partition',
7 estimate_percent => null);
8 end;
9 /
PL/SQL procedure successfully completed.
SQL> select table_name, partition_name, num_rows from user_tab_partitions where table_name='T' order by partition_name;
TABLE_NAME                 PARTITION_NAME               NUM_ROWS
T                      P01                       50000
T                      P02                       50000
T                      P03                       50000
T                      PXX                       50000Now let's say you only want to index P01.
You could do it as follows :SQL> create index t_idx on t(decode(grp,1,id,null)) local;
Index created.The index would only have IDs from partition P01.
SQL> select INDEX_NAME, PARTITION_NAME, DISTINCT_KEYS
2 from user_ind_partitions
3 where index_name='T_IDX'
4 order by partition_name;
INDEX_NAME                 PARTITION_NAME                DISTINCT_KEYS
T_IDX                      P01                          50000
T_IDX                      P02                           0
T_IDX                      P03                           0
T_IDX                      PXX                           0
SQL> select SEGMENT_NAME, PARTITION_NAME, BYTES
2 from user_segments
3 where SEGMENT_NAME='T_IDX'
4 order by partition_name;
SEGMENT_NAME                                               PARTITION_NAME                BYTES
T_IDX                                                    P01                        1048576
T_IDX                                                    P02                          65536
T_IDX                                                    P03                          65536
T_IDX                                                    PXX                          65536See, only the keys from P01 are here, and only the segment for P01 partition has grown <i>(the 65k segment for the others partitions come from default values of storage clause which I didn't specify)</i>.
Now you can query your table in the following way.
Instead of writing (for P01) : select * from t where grp=1 and id between 30 and 40;If you want to use the index on P01, you would do :SQL> select * from t where grp=1 and decode(grp,1,id,null) between 30 and 40;
       GRP        ID VAL
      1        32 hSrmmTYXXW
      1        36 xofKlsxORE
      1        40 vazRGnWzWc
Execution Plan
Plan hash value: 1186642050
| Id | Operation                  | Name | Rows | Bytes | Cost (%CPU)| Time        | Pstart| Pstop |
|   0 | SELECT STATEMENT             |        |   125 | 2375 |      3   (0)| 00:00:01 |        |        |
|   1 | PARTITION RANGE SINGLE         |        |   125 | 2375 |      3   (0)| 00:00:01 |      1 |      1 |
|* 2 |   TABLE ACCESS BY LOCAL INDEX ROWID| T        |   125 | 2375 |      3   (0)| 00:00:01 |      1 |      1 |
|* 3 |    INDEX RANGE SCAN             | T_IDX |   225 |        |      2   (0)| 00:00:01 |      1 |      1 |
Predicate Information (identified by operation id):
   2 - filter("GRP"=1)
   3 - access(DECODE("GRP",1,"ID",NULL)>=30 AND DECODE("GRP",1,"ID",NULL)<=40)The index is being used.
+(also note that the grp value is "given" twice in the query : once explicitly, the other one within the decode.)+
Now for a query like : SQL> select * from t where grp=2 and id between 30 and 40;
       GRP        ID VAL
      2        33 bhFrCYCiDb
      2        37 jnPauHJiyo
Execution Plan
Plan hash value: 2931986080
| Id | Operation            | Name | Rows | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
|   0 | SELECT STATEMENT       |      |     5 |    95 |    68     (0)| 00:00:01 |       |       |
|   1 | PARTITION RANGE SINGLE|      |     5 |    95 |    68     (0)| 00:00:01 |     2 |     2 |
|* 2 |   TABLE ACCESS FULL    | T    |     5 |    95 |    68     (0)| 00:00:01 |     2 |     2 |
Predicate Information (identified by operation id):
   2 - filter("ID"<=40 AND "ID">=30 AND "GRP"=2)The optimizer goes for a FULL TABLE (partition) SCAN.
<b>NOTE :</b> That would also work with a global index.
Of course, it remains a rather dirty tweak...
;-)

I want information in practical sceario how to create indexes?

hi,
i want complete information about indexes? how create indexes in real time?

" Secondary Database
First it must be stated that table design is a more logical work while index design is rather technical. In table design it might make sense to place certain fields (client, company code, ...) in the beginning. In index design, this is not advisable. Very important for an index is that it contains very selective fields in the beginning. Those are fields like object numbers. Not selective are client, company code, ...
Indexes should be small (few fields). The Database optimizer can combine two or more indexes to execute a query.
Indexes of one table should be disjoint (have few common fields), in order not to confuse the optimizer which index to use.
Note that each index slows the inserts into the table down. Updates are only slowed down if indexed fields are updated. In general, heavy inserted tables should have only few indexes while heavy selected tables might have more.
" Creating Secondary Indexes
Procedure
1.In the maintenance screen of the table, choose Indexes.
If indexes already exist on the table, a list of these indexes is displayed. Choose .
2.In the next dialog box, enter the index ID and choose
The maintenance screen for indexes appears.
3.Enter an explanatory text in the field Short text.
You can then use the short text to find the index at a later time, for example with the R/3 Repository Information System.
4.Select the table fields to be included in the index using the input help for the Field name column.
The order of the fields in the index is very important. See What to Keep in Mind for Secondary Indexes.
5.If the values in the index fields already uniquely identify each record of the table, select Unique index.
A unique index is always created in the database at activation because it also has a functional meaning (prevents double entries of the index fields).
6.If it is not a unique index, leave Non-unique index selected.
In this case you can use the radio buttons to define whether the index should be created for all database systems, for selected database systems or not at all in the database.
7.Select for selected database systems if the index should only be created for selected database systems.
Click on the arrow behind the radio buttons. A dialog box appears in which you can define up to 4 database systems with the input help. Select Selection list if the index should only be created on the given database systems. Select Exclusion list if the index should not be created on the given database systems. Choose .
8.Choose activate.
" Result
The secondary index is automatically created in the database during activation if the corresponding table was already created there and index creation was not excluded for the database system.
You can find information about the activation flow in the activation log, which you can call with Utilities ® Activation log. If errors occurred when activating the index, the activation log is automatically displayed.
" How to Check if an Index is Used
Procedure
1.Open a second session and choose System -> Utilities ->Performance trace.
The Trace Requests screen appears.
2.Select Trace on.
The SQL trace is activated for your user, that is all the database operations under your user are recorded.
3.In the first window, perform the action in which the index should be used.
If your database system uses a cost-based optimizer, you should perform this action with as representative data as possible. A cost-based optimizer tries to determine the best index based on the statistics.
4.In the second session, choose Trace off and then Trace list.
Result
The format of the generated output depends on the database system used. You can determine the index that the database used for your action with the EXPLAIN function for the critical statements (PREPARE, OPEN, REPOPEN).
" What to Keep in Mind for Secondary Indexes
How well an existing index supports data selection from a table largely depends on whether the data selected with the index represents the data that will ultimately be selected. This can best be shown using an example.
' Example :
An index is defined on fields FIELD1, FIELD2, FIELD3 and FIELD4 of table BSPTAB in this order. This table is accessed with the SELECT statement:
SELECT * FROM BSPTAB WHERE FIELD1 = X1 AND FIELD2 = X2 AND FIELD4= X4.
Since FIELD3 is not specified more exactly, only the index sorting up to FIELD2 is of any use. If the database system accesses the data using this index, it will quickly find all the records for which FIELD1 = X1 and FIELD2 = X2. You then have to select all the records for which FIELD4 = X4 from this set.
The order of the fields in the index is very important for the accessing speed. The first fields should be those which have constant values for a large number of selections. During selection, an index is only of use up to the first unspecified field.
Only those fields that significantly restrict the set of results in a selection make sense for an index.
Reward points if it is usefull.....
Girish

How to create index on a varchar column that represent date?

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