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Oracle® Database SQL Language Reference
11g Release 2 (11.2)

Part Number E17118-03
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CREATE INDEX

Purpose

Use the CREATE INDEX statement to create an index on:

An index is a schema object that contains an entry for each value that appears in the indexed column(s) of the table or cluster and provides direct, fast access to rows. Oracle Database supports several types of index:

See Also:

Additional Topics

Prerequisites

To create an index in your own schema, one of the following conditions must be true:

To create an index in another schema, you must have the CREATE ANY INDEX system privilege. Also, the owner of the schema to contain the index must have either the UNLIMITED TABLESPACE system privilege or space quota on the tablespaces to contain the index or index partitions.

To create a domain index in your own schema, in addition to the prerequisites for creating a conventional index, you must also have the EXECUTE object privilege on the indextype. If you are creating a domain index in another user's schema, then the index owner also must have the EXECUTE object privilege on the indextype and its underlying implementation type. Before creating a domain index, you should first define the indextype.

To create a function-based index, in addition to the prerequisites for creating a conventional index, if the index is based on user-defined functions, then those functions must be marked DETERMINISTIC. Also, you must have the EXECUTE object privilege on any user-defined function(s) used in the function-based index if those functions are owned by another user.

See Also:

CREATE INDEXTYPE

Syntax

create_index::=

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Description of the illustration create_index.gif

cluster_index_clause ::=

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Description of the illustration cluster_index_clause.gif

(index_attributes::=)

table_index_clause ::=

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Description of the illustration table_index_clause.gif

(index_properties::=)

bitmap_join_index_clause ::=

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Description of the illustration bitmap_join_index_clause.gif

(local_partitioned_index ::=, index_attributes::=)

index_expr::=

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Description of the illustration index_expr.gif

index_properties::=

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(global_partitioned_index::=, local_partitioned_index ::=, index_attributes::=, domain_index_clause ::=, XMLIndex_clause::=)

index_attributes::=

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Description of the illustration index_attributes.gif

(physical_attributes_clause ::=, logging_clause::=, key_compression::=, parallel_clause::=)

physical_attributes_clause ::=

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Description of the illustration physical_attributes_clause.gif

(storage_clause::=)

logging_clause::=

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key_compression::=

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Description of the illustration key_compression.gif

domain_index_clause ::=

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Description of the illustration domain_index_clause.gif

(parallel_clause::=)

local_domain_index_clause::=

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Description of the illustration local_domain_index_clause.gif

XMLIndex_clause::=

Description of xmlindex_clause.gif follows
Description of the illustration xmlindex_clause.gif

( The XMLIndex_parameters_clause is documented in Oracle XML DB Developer's Guide.)

local_XMLIndex_clause::=

Description of local_xmlindex_clause.gif follows
Description of the illustration local_xmlindex_clause.gif

global_partitioned_index::=

Description of global_partitioned_index.gif follows
Description of the illustration global_partitioned_index.gif

(index_partitioning_clause::=, individual_hash_partitions::=, hash_partitions_by_quantity::=)

individual_hash_partitions::=

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Description of the illustration individual_hash_partitions.gif

(partitioning_storage_clause::=)

partitioning_storage_clause::=

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Description of the illustration partitioning_storage_clause.gif

LOB_partitioning_storage::=

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Description of the illustration lob_partitioning_storage.gif

hash_partitions_by_quantity::=

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Description of the illustration hash_partitions_by_quantity.gif

index_partitioning_clause::=

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Description of the illustration index_partitioning_clause.gif

(segment_attributes_clause::=)

local_partitioned_index ::=

Description of local_partitioned_index.gif follows
Description of the illustration local_partitioned_index.gif

(on_range_partitioned_table ::=, on_list_partitioned_table::=, on_hash_partitioned_table ::=, on_comp_partitioned_table ::=)

on_range_partitioned_table ::=

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Description of the illustration on_range_partitioned_table.gif

(segment_attributes_clause::=)

on_list_partitioned_table::=

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Description of the illustration on_list_partitioned_table.gif

(segment_attributes_clause::=)

segment_attributes_clause::=

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Description of the illustration segment_attributes_clause.gif

(physical_attributes_clause ::=, logging_clause::=

on_hash_partitioned_table ::=

Description of on_hash_partitioned_table.gif follows
Description of the illustration on_hash_partitioned_table.gif

on_comp_partitioned_table ::=

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Description of the illustration on_comp_partitioned_table.gif

(segment_attributes_clause::=, index_subpartition_clause::=)

index_subpartition_clause::=

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Description of the illustration index_subpartition_clause.gif

parallel_clause::=

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Description of the illustration parallel_clause.gif

(storage_clause::=)

Semantics

UNIQUE

Specify UNIQUE to indicate that the value of the column (or columns) upon which the index is based must be unique.

Restrictions on Unique Indexes Unique indexes are subject to the following restrictions:

See Also:

"Unique Constraints" for information on the conditions that satisfy a unique constraint

BITMAP

Specify BITMAP to indicate that index is to be created with a bitmap for each distinct key, rather than indexing each row separately. Bitmap indexes store the rowids associated with a key value as a bitmap. Each bit in the bitmap corresponds to a possible rowid. If the bit is set, then it means that the row with the corresponding rowid contains the key value. The internal representation of bitmaps is best suited for applications with low levels of concurrent transactions, such as data warehousing.

Note:

Oracle does not index table rows in which all key columns are null except in the case of bitmap indexes. Therefore, if you want an index on all rows of a table, then you must either specify NOT NULL constraints for the index key columns or create a bitmap index.

Restrictions on Bitmap Indexes Bitmap indexes are subject to the following restrictions:

See Also:

schema

Specify the schema to contain the index. If you omit schema, then Oracle Database creates the index in your own schema.

index

Specify the name of the index to be created.

cluster_index_clause

Use the cluster_index_clause to identify the cluster for which a cluster index is to be created. If you do not qualify cluster with schema, then Oracle Database assumes the cluster is in your current schema. You cannot create a cluster index for a hash cluster.

table_index_clause

Specify the table on which you are defining the index. If you do not qualify table with schema, then Oracle Database assumes the table is contained in your own schema.

You create an index on a nested table column by creating the index on the nested table storage table. Include the NESTED_TABLE_ID pseudocolumn of the storage table to create a UNIQUE index, which effectively ensures that the rows of a nested table value are distinct.

You can perform DDL operations (such as ALTER TABLE, DROP TABLE, CREATE INDEX) on a temporary table only when no session is bound to it. A session becomes bound to a temporary table by performing an INSERT operation on the table. A session becomes unbound to the temporary table by issuing a TRUNCATE statement or at session termination, or, for a transaction-specific temporary table, by issuing a COMMIT or ROLLBACK statement.

Restrictions on the table_index_clause This clause is subject to the following restrictions:

See Also:

CREATE TABLE and Oracle Database Concepts for more information on temporary tables

t_alias

Specify a correlation name (alias) for the table upon which you are building the index.

Note:

This alias is required if the index_expr references any object type attributes or object type methods. See "Creating a Function-based Index on a Type Method: Example" and "Indexing on Substitutable Columns: Examples".

index_expr

For index_expr, specify the column or column expression upon which the index is based.

column  Specify the name of one or more columns in the table. A bitmap index can have a maximum of 30 columns. Other indexes can have as many as 32 columns. These columns define the index key.

If a unique index is local nonprefixed (see local_partitioned_index ), then the index key must contain the partitioning key.

See Also:

Oracle Database VLDB and Partitioning Guide for information on prefixed and nonprefixed indexes

You can create an index on a scalar object attribute column or on the system-defined NESTED_TABLE_ID column of the nested table storage table. If you specify an object attribute column, then the column name must be qualified with the table name. If you specify a nested table column attribute, then it must be qualified with the outermost table name, the containing column name, and all intermediate attribute names leading to the nested table column attribute.

Restriction on Index Columns You cannot create an index on columns or attributes whose type is user-defined, LONG, LONG RAW, LOB, or REF, except that Oracle Database supports an index on REF type columns or attributes that have been defined with a SCOPE clause.

column_expression Specify an expression built from columns of table, constants, SQL functions, and user-defined functions. When you specify column_expression, you create a function-based index.

Name resolution of the function is based on the schema of the index creator. User-defined functions used in column_expression are fully name resolved during the CREATE INDEX operation.

After creating a function-based index, collect statistics on both the index and its base table using the DBMS_STATS package. Such statistics will enable Oracle Database to correctly decide when to use the index.

Function-based unique indexes can be useful in defining a conditional unique constraint on a column or combination of columns. Refer to "Using a Function-based Index to Define Conditional Uniqueness: Example" for an example.

See Also:

Oracle Database PL/SQL Packages and Types Reference for more information on the DBMS_STATS package

Notes on Function-based Indexes The following notes apply to function-based indexes:

Restrictions on Function-based Indexes Function-based indexes are subject to the following restrictions:

ASC | DESC

Use ASC or DESC to indicate whether the index should be created in ascending or descending order. Indexes on character data are created in ascending or descending order of the character values in the database character set.

Oracle Database treats descending indexes as if they were function-based indexes. As with other function-based indexes, the database does not use descending indexes until you first analyze the index and the table on which the index is defined. See the column_expression clause of this statement.

Ascending unique indexes allow multiple NULL values. However, in descending unique indexes, multiple NULL values are treated as duplicate values and therefore are not permitted.

Restriction on Ascending and Descending Indexes You cannot specify either of these clauses for a domain index. You cannot specify DESC for a reverse index. Oracle Database ignores DESC if index is bitmapped or if the COMPATIBLE initialization parameter is set to a value less than 8.1.0.

index_attributes

Specify the optional index attributes.

physical_attributes_clause  Use the physical_attributes_clause to establish values for physical and storage characteristics for the index.

If you omit this clause, then Oracle Database sets PCTFREE to 10 and INITRANS to 2.

Restriction on Index Physical Attributes You cannot specify the PCTUSED parameter for an index.

See Also:

physical_attributes_clause and storage_clause for a complete description of these clauses

TABLESPACE For tablespace, specify the name of the tablespace to hold the index, index partition, or index subpartition. If you omit this clause, then Oracle Database creates the index in the default tablespace of the owner of the schema containing the index.

For a local index, you can specify the keyword DEFAULT in place of tablespace. New partitions or subpartitions added to the local index will be created in the same tablespace(s) as the corresponding partitions or subpartitions of the underlying table.

key_compression Specify COMPRESS to enable key compression, which eliminates repeated occurrence of key column values and may substantially reduce storage. Use integer to specify the prefix length (number of prefix columns to compress).

Oracle Database compresses indexes that are nonunique or unique indexes of at least two columns. If you want to use compression for a partitioned index, then you must create the index with compression enabled at the index level. You can subsequently enable and disable the compression setting for individual partitions of such a partitioned index. You can also enable and disable compression when rebuilding individual partitions. You can modify an existing non-partitioned index to enable or disable compression only when rebuilding the index.

Restriction on Key Compression You cannot specify COMPRESS for a bitmap index.

NOCOMPRESS  Specify NOCOMPRESS to disable key compression. This is the default.

SORT | NOSORT  By default, Oracle Database sorts indexes in ascending order when it creates the index. You can specify NOSORT to indicate to the database that the rows are already stored in the database in ascending order, so that Oracle Database does not have to sort the rows when creating the index. If the rows of the indexed column or columns are not stored in ascending order, then the database returns an error. For greatest savings of sort time and space, use this clause immediately after the initial load of rows into a table. If you specify neither of these keywords, then SORT is the default.

Restrictions on NOSORT This parameter is subject to the following restrictions:

REVERSE  Specify REVERSE to store the bytes of the index block in reverse order, excluding the rowid.

Restrictions on Reverse Indexes Reverse indexes are subject to the following restrictions:

VISIBLE | INVISIBLE  Use this clause to specify whether the index is visible or invisible to the optimizer. An invisible index is maintained by DML operations, but it is not be used by the optimizer during queries unless you explicitly set the parameter OPTIMIZER_USE_INVISIBLE_INDEXES to TRUE at the session or system level.

To determine whether an existing index is visible or invisible to the optimizer, you can query the VISIBILITY column of the USER_, DBA_, ALL_INDEXES data dictionary views.

See Also:

Oracle Database Administrator's Guide for more information on this feature

logging_clause Specify whether the creation of the index will be logged (LOGGING) or not logged (NOLOGGING) in the redo log file. This setting also determines whether subsequent Direct Loader (SQL*Loader) and direct-path INSERT operations against the index are logged or not logged. LOGGING is the default.

If index is nonpartitioned, then this clause specifies the logging attribute of the index.

If index is partitioned, then this clause determines:

The logging attribute of the index is independent of that of its base table.

If you omit this clause, then the logging attribute is that of the tablespace in which it resides.

See Also:

ONLINE  Specify ONLINE to indicate that DML operations on the table will be allowed during creation of the index.

Restrictions on Online Index Building Online index building is subject to the following restrictions:

See Also:

Oracle Database Concepts for a description of online index building and rebuilding

parallel_clause

Specify the parallel_clause if you want creation of the index to be parallelized.

For complete information on this clause, refer to parallel_clause in the documentation on CREATE TABLE.

Index Partitioning Clauses

Use the global_partitioned_index clause and the local_partitioned_index clauses to partition index.

The storage of partitioned database entities in tablespaces of different block sizes is subject to several restrictions. Please refer to Oracle Database VLDB and Partitioning Guide for a discussion of these restrictions.

global_partitioned_index

The global_partitioned_index clause lets you specify that the partitioning of the index is user defined and is not equipartitioned with the underlying table. By default, nonpartitioned indexes are global indexes.

You can partition a global index by range or by hash. In both cases, you can specify up to 32 columns as partitioning key columns. The partitioning column list must specify a left prefix of the index column list. If the index is defined on columns a, b, and c, then for the columns you can specify (a, b, c), or (a, b), or (a, c), but you cannot specify (b, c) or (c) or (b, a). If you omit the partition names, then Oracle Database assigns names of the form SYS_Pn.

GLOBAL PARTITION BY RANGE Use this clause to create a range-partitioned global index. Oracle Database will partition the global index on the ranges of values from the table columns you specify in the column list.

GLOBAL PARTITION BY HASH Use this clause to create a hash-partitioned global index. Oracle Database assigns rows to the partitions using a hash function on values in the partitioning key columns.

See Also:

The CREATE TABLE clause hash_partitions for information on the two methods of hash partitioning and "Creating a Hash-Partitioned Global Index: Example"

Restrictions on Global Partitioned Indexes Global partitioned indexes are subject to the following restrictions:

Note:

If your enterprise has or will have databases using different character sets, then use caution when partitioning on character columns. The sort sequence of characters is not identical in all character sets.

See Also:

Oracle Database Globalization Support Guide for more information on character set support

index_partitioning_clause Use this clause to describe the individual index partitions. The number of repetitions of this clause determines the number of partitions. If you omit partition, then Oracle Database generates a name with the form SYS_Pn.

For VALUES LESS THAN (value_list), specify the noninclusive upper bound for the current partition in a global index. The value list is a comma-delimited, ordered list of literal values corresponding to the column list in the global_partitioned_index clause. Always specify MAXVALUE as the value of the last partition.

Note:

If the index is partitioned on a DATE column, and if the date format does not specify the first two digits of the year, then you must use the TO_DATE function with a 4-character format mask for the year. The date format is determined implicitly by NLS_TERRITORY or explicitly by NLS_DATE_FORMAT. Refer to Oracle Database Globalization Support Guide for more information on these initialization parameters.

local_partitioned_index

The local_partitioned_index clauses let you specify that the index is partitioned on the same columns, with the same number of partitions and the same partition bounds as table. Oracle Database automatically maintains local index partitioning as the underlying table is repartitioned.

on_range_partitioned_table  This clause lets you specify the names and attributes of index partitions on a range-partitioned table. If you specify this clause, then the number of PARTITION clauses must be equal to the number of table partitions, and in the same order. If you omit partition, then Oracle Database generates a name that is consistent with the corresponding table partition. If the name conflicts with an existing index partition name, then the database uses the form SYS_Pn.

You cannot specify key compression for an index partition unless you have specified key compression for the index.

For more information on the UNUSABLE clause, refer to UNUSABLE.

on_list_partitioned_table The on_list_partitioned_table clause is identical to on_range_partitioned_table .

on_hash_partitioned_table  This clause lets you specify names and tablespace storage for index partitions on a hash-partitioned table.

If you specify any PARTITION clauses, then the number of these clauses must be equal to the number of table partitions. If you omit partition, then Oracle Database generates a name that is consistent with the corresponding table partition. If the name conflicts with an existing index partition name, then the database uses the form SYS_Pn. You can optionally specify tablespace storage for one or more individual partitions. If you do not specify tablespace storage either here or in the STORE IN clause, then the database stores each index partition in the same tablespace as the corresponding table partition.

The STORE IN clause lets you specify one or more tablespaces across which Oracle Database will distribute all the index hash partitions. The number of tablespaces need not equal the number of index partitions. If the number of index partitions is greater than the number of tablespaces, then the database cycles through the names of the tablespaces.

on_comp_partitioned_table  This clause lets you specify the name and attributes of index partitions on a composite-partitioned table.

The STORE IN clause is valid only for range-hash or list-hash composite-partitioned tables. It lets you specify one or more default tablespaces across which Oracle Database will distribute all index hash subpartitions for all partitions. You can override this storage by specifying different default tablespace storage for the subpartitions of an individual partition in the second STORE IN clause in the index_subpartition_clause.

For range_range, range-list, and list-list composite-partitioned tables, you can specify default attributes for the range or list subpartitions in the PARTITION clause. You can override this storage by specifying different attributes for the range or list subpartitions of an individual partition in the SUBPARTITION clause of the index_subpartition_clause.

You cannot specify key compression for an index partition unless you have specified key compression for the index.

For more information on the UNUSABLE clause, refer to UNUSABLE.

index_subpartition_clause This clause lets you specify names and tablespace storage for index subpartitions in a composite-partitioned table.

The STORE IN clause is valid only for hash subpartitions of a range-hash and list-hash composite-partitioned table. It lets you specify one or more tablespaces across which Oracle Database will distribute all the index hash subpartitions. The SUBPARTITION clause is valid for all subpartition types.

If you specify any SUBPARTITION clauses, then the number of those clauses must be equal to the number of table subpartitions. If you omit subpartition, then the database generates a name that is consistent with the corresponding table subpartition. If the name conflicts with an existing index subpartition name, then the database uses the form SYS_SUBPn.

The number of tablespaces need not equal the number of index subpartitions. If the number of index subpartitions is greater than the number of tablespaces, then the database cycles through the names of the tablespaces.

If you do not specify tablespace storage for subpartitions either in the on_comp_partitioned_table clause or in the index_subpartition_clause, then Oracle Database uses the tablespace specified for index. If you also do not specify tablespace storage for index, then the database stores the subpartition in the same tablespace as the corresponding table subpartition.

For more information on the UNUSABLE clause, refer to CREATE INDEX ... UNUSABLE.

domain_index_clause

Use the domain_index_clause to indicate that index is a domain index, which is an instance of an application-specific index of type indextype.

Creating a domain index requires a number of preceding operations. You must first create an implementation type for an indextype. You must also create a functional implementation and then create an operator that uses the function. Next you create an indextype, which associates the implementation type with the operator. Finally, you create the domain index using this clause. Refer to Appendix F, "Extended Examples", which contains an example of creating a simple domain index, including all of these operations.

index_expr In the index_expr (in table_index_clause), specify the table columns or object attributes on which the index is defined. You can define multiple domain indexes on a single column only if the underlying indextypes are different and the indextypes support a disjoint set of user-defined operators.

Restrictions on Domain Indexes Domain indexes are subject to the following restrictions:

indextype For indextype, specify the name of the indextype. This name should be a valid schema object that has already been created.

If you have installed Oracle Text, then you can use various built-in indextypes to create Oracle Text domain indexes. For more information on Oracle Text and the indexes it uses, refer to Oracle Text Reference.

See Also:

CREATE INDEXTYPE

local_domain_index_clause Use this clause to specify that the index is a local index on a partitioned table.

parallel_clause  Use the parallel_clause to parallelize creation of the domain index. For a nonpartitioned domain index, Oracle Database passes the explicit or default degree of parallelism to the ODCIIndexCreate cartridge routine, which in turn establishes parallelism for the index. For local domain indexes, this clause causes the index partitions to be created in parallel.

See Also:

Oracle Database Data Cartridge Developer's Guide for complete information on the Oracle Data Cartridge Interface (ODCI) routines

PARAMETERS In the PARAMETERS clause, specify the parameter string that is passed uninterpreted to the appropriate ODCI indextype routine. The maximum length of the parameter string is 1000 characters.

When you specify this clause at the top level of the syntax, the parameters become the default parameters for the index partitions. If you specify this clause as part of the local_domain_index_clause, then you override any default parameters with parameters for the individual partition.

After the domain index is created, Oracle Database invokes the appropriate ODCI routine. If the routine does not return successfully, then the domain index is marked FAILED. The only operations supported on an failed domain index are DROP INDEX and (for non-local indexes) REBUILD INDEX.

See Also:

Oracle Database Data Cartridge Developer's Guide for information on the Oracle Data Cartridge Interface (ODCI) routines

XMLIndex_clause

The XMLIndex_clause lets you define an XMLIndex index, typically on a column contain XML data. An XMLIndex index is a type of domain index designed specifically for the domain of XML data.

XMLIndex_parameters_clause 

This clause lets you specify information about the path table and about the secondary indexes corresponding to the components of XMLIndex. This clause also lets you specify information about the structured component of the index. The maximum length of the parameter string is 1000 characters.

When you specify this clause at the top level of the syntax, the parameters become the parameters of the index and the default parameters for the index partitions. If you specify this clause as part of the local_xmlindex_clause clause, then you override any default parameters with parameters for the individual partition.

See Also:

Oracle XML DB Developer's Guide for the syntax and semantics of the XMLIndex_parameters_clause clause, as well as detailed information about the use of XMLIndex

bitmap_join_index_clause

Use the bitmap_join_index_clause to define a bitmap join index. A bitmap join index is defined on a single table. For an index key made up of dimension table columns, it stores the fact table rowids corresponding to that key. In a data warehousing environment, the table on which the index is defined is commonly referred to as a fact table, and the tables with which this table is joined are commonly referred to as dimension tables. However, a star schema is not a requirement for creating a join index.

ON In the ON clause, first specify the fact table, and then inside the parentheses specify the columns of the dimension tables on which the index is defined.

FROM In the FROM clause, specify the joined tables.

WHERE In the WHERE clause, specify the join condition.

If the underlying fact table is partitioned, then you must also specify one of the local_partitioned_index clauses (see local_partitioned_index ).

Restrictions on Bitmap Join Indexes In addition to the restrictions on bitmap indexes in general (see BITMAP), the following restrictions apply to bitmap join indexes:

See Also:

Oracle Database Data Warehousing Guide for information on fact and dimension tables and on using bitmap indexes in a data warehousing environment

UNUSABLE

Specify UNUSABLE to create an index in an UNUSABLE state. An unusable index must be rebuilt, or dropped and re-created, before it can be used.

If the index is partitioned, then all index partitions are marked UNUSABLE. You can then subsequently choose to rebuild only some of the index partitions to make them USABLE. Doing so can be useful if you want to maintain indexes only on some index partitions—for example, if you want to enable index access for new partitions but not for old partitions.

When an index, or some partitions or subpartitions of an index, are created UNUSABLE, no segment is allocated for the unusable object. The unusable index or index partition consumes no space in the database.

If an index, or some partitions or subpartitions of the index, are marked UNUSABLE, then the index will be considered as an access path by the optimizer only under the following circumstances: the optimizer must know at compile time which partitions are to be accessed, and all of those partitions to be accessed must be marked USABLE. Therefore, the query cannot contain any bind variables.

Restrictions on UNUSABLE The following restrictions apply when marking an index UNUSABLE:

Examples

General Index Examples

Creating an Index: Example The following statement shows how the sample index ord_customer_ix on the customer_id column of the sample table oe.orders was created:

CREATE INDEX ord_customer_ix
   ON orders (customer_id);

Compressing an Index: Example To create the ord_customer_ix_demo index with the COMPRESS clause, you might issue the following statement:

CREATE INDEX ord_customer_ix_demo 
   ON orders (customer_id, sales_rep_id)
   COMPRESS 1;

The index will compress repeated occurrences of customer_id column values.

Creating an Index in NOLOGGING Mode: Example If the sample table orders had been created using a fast parallel load (so all rows were already sorted), then you could issue the following statement to quickly create an index.

/* Unless you first sort the table oe.orders, this example fails
   because you cannot specify NOSORT unless the base table is
   already sorted.
*/
CREATE INDEX ord_customer_ix_demo
   ON orders (order_mode)
   NOSORT
   NOLOGGING;

Creating a Cluster Index: Example To create an index for the personnel cluster, which was created in "Creating a Cluster: Example", issue the following statement:

CREATE INDEX idx_personnel ON CLUSTER personnel; 

No index columns are specified, because cluster indexes are automatically built on all the columns of the cluster key. For cluster indexes, all rows are indexed.

Creating an Index on an XMLType Table: Example The following example creates an index on the area element of the xwarehouses table (created in "XMLType Table Examples"):

CREATE INDEX area_index ON xwarehouses e 
   (EXTRACTVALUE(VALUE(e),'/Warehouse/Area'));

Such an index would greatly improve the performance of queries that select from the table based on, for example, the square footage of a warehouse, as shown in this statement:

SELECT e.getClobVal() AS warehouse
   FROM xwarehouses e
   WHERE EXISTSNODE(VALUE(e),'/Warehouse[Area>50000]') = 1;

See Also:

EXISTSNODE and VALUE

Function-Based Index Examples

The following examples show how to create and use function-based indexes.

Creating a Function-Based Index: Example The following statement creates a function-based index on the employees table based on an uppercase evaluation of the last_name column:

CREATE INDEX upper_ix ON employees (UPPER(last_name)); 

See the "Prerequisites" for the privileges and parameter settings required when creating function-based indexes.

To ensure that Oracle Database will use the index rather than performing a full table scan, be sure that the value returned by the function is not null in subsequent queries. For example, this statement is guaranteed to use the index:

SELECT first_name, last_name 
   FROM employees WHERE UPPER(last_name) IS NOT NULL
   ORDER BY UPPER(last_name);

Without the WHERE clause, Oracle Database may perform a full table scan.

In the next statements showing index creation and subsequent query, Oracle Database will use index income_ix even though the columns are in reverse order in the query:

CREATE INDEX income_ix 
   ON employees(salary + (salary*commission_pct));

SELECT first_name||' '||last_name "Name"
   FROM employees 
   WHERE (salary*commission_pct) + salary > 15000
   ORDER BY employee_id;

Creating a Function-Based Index on a LOB Column: Example The following statement uses the text_length function to create a function-based index on a LOB column in the sample pm schema. See Oracle Database PL/SQL Language Reference for the example that creates this function. The example selects rows from the sample table print_media where that CLOB column has fewer than 1000 characters.

CREATE INDEX src_idx ON print_media(text_length(ad_sourcetext));

SELECT product_id FROM print_media 
   WHERE text_length(ad_sourcetext) < 1000
   ORDER BY product_id;

PRODUCT_ID
----------
      2056
      2268
      3060
      3106

Creating a Function-based Index on a Type Method: Example This example entails an object type rectangle containing two number attributes: length and width. The area() method computes the area of the rectangle.

CREATE TYPE rectangle AS OBJECT  
( length   NUMBER, 
  width    NUMBER, 
  MEMBER FUNCTION area RETURN NUMBER DETERMINISTIC 
); 
 
CREATE OR REPLACE TYPE BODY rectangle AS 
  MEMBER FUNCTION area RETURN NUMBER IS 
  BEGIN 
   RETURN (length*width); 
  END; 
END; 

Now, if you create a table rect_tab of type rectangle, you can create a function-based index on the area() method as follows:

CREATE TABLE rect_tab OF rectangle; 
CREATE INDEX area_idx ON rect_tab x (x.area()); 

You can use this index efficiently to evaluate a query of the form:

SELECT * FROM rect_tab x WHERE x.area() > 100; 

Using a Function-based Index to Define Conditional Uniqueness: Example  The following statement creates a unique function-based index on the oe.orders table that prevents a customer from taking advantage of promotion ID 2 ("blowout sale") more than once:

CREATE UNIQUE INDEX promo_ix ON orders
   (CASE WHEN promotion_id =2 THEN customer_id ELSE NULL END,
    CASE WHEN promotion_id = 2 THEN promotion_id ELSE NULL END);

INSERT INTO orders (order_id, order_date, customer_id, order_total, promotion_id)
   VALUES (2459, systimestamp, 106, 251, 2);
1 row created.

INSERT INTO orders (order_id, order_date, customer_id, order_total, promotion_id)
   VALUES (2460, systimestamp+1, 106, 110, 2);
insert into orders (order_id, order_date, customer_id, order_total, promotion_id)
*
ERROR at line 1:
ORA-00001: unique constraint (OE.PROMO_IX) violated

The objective is to remove from the index any rows where the promotion_id is not equal to 2. Oracle Database does not store in the index any rows where all the keys are NULL. Therefore, in this example, both customer_id and promotion_id are mapped to NULL unless promotion_id is equal to 2. The result is that the index constraint is violated only if promotion_id is equal to 2 for two rows with the same customer_id value.

Partitioned Index Examples

Creating a Range-Partitioned Global Index: Example The following statement creates a global prefixed index cost_ix on the sample table sh.sales with three partitions that divide the range of costs into three groups:

CREATE INDEX cost_ix ON sales (amount_sold)
   GLOBAL PARTITION BY RANGE (amount_sold)
      (PARTITION p1 VALUES LESS THAN (1000),
       PARTITION p2 VALUES LESS THAN (2500),
       PARTITION p3 VALUES LESS THAN (MAXVALUE));

Creating a Hash-Partitioned Global Index: Example The following statement creates a hash-partitioned global index cust_last_name_ix on the sample table sh.customers with four partitions:

CREATE INDEX cust_last_name_ix ON customers (cust_last_name)
  GLOBAL PARTITION BY HASH (cust_last_name)
  PARTITIONS 4;

Creating an Index on a Hash-Partitioned Table: Example The following statement creates a local index on the category_id column of the hash_products partitioned table (which was created in "Hash Partitioning Example"). The STORE IN clause immediately following LOCAL indicates that hash_products is hash partitioned. Oracle Database will distribute the hash partitions between the tbs1 and tbs2 tablespaces:

CREATE INDEX prod_idx ON hash_products(category_id) LOCAL
   STORE IN (tbs_01, tbs_02);

The creator of the index must have quota on the tablespaces specified. See CREATE TABLESPACE for examples that create tablespaces tbs_1 and tbs_2.

Creating an Index on a Composite-Partitioned Table: Example The following statement creates a local index on the composite_sales table, which was created in "Composite-Partitioned Table Examples". The STORAGE clause specifies default storage attributes for the index. However, this default is overridden for the five subpartitions of partitions q3_2000 and q4_2000, because separate TABLESPACE storage is specified.

The creator of the index must have quota on the tablespaces specified. See CREATE TABLESPACE for examples that create tablespaces tbs_1 and tbs_2.

CREATE INDEX sales_ix ON composite_sales(time_id, prod_id)
   STORAGE (INITIAL 1M)
   LOCAL
   (PARTITION q1_1998,
    PARTITION q2_1998,
    PARTITION q3_1998,
    PARTITION q4_1998,
    PARTITION q1_1999,
    PARTITION q2_1999,
    PARTITION q3_1999,
    PARTITION q4_1999,
    PARTITION q1_2000,
    PARTITION q2_2000
      (SUBPARTITION pq2001, SUBPARTITION pq2002, 
       SUBPARTITION pq2003, SUBPARTITION pq2004,
       SUBPARTITION pq2005, SUBPARTITION pq2006, 
       SUBPARTITION pq2007, SUBPARTITION pq2008),
    PARTITION q3_2000
      (SUBPARTITION c1 TABLESPACE tbs_02, 
       SUBPARTITION c2 TABLESPACE tbs_02, 
       SUBPARTITION c3 TABLESPACE tbs_02,
       SUBPARTITION c4 TABLESPACE tbs_02,
       SUBPARTITION c5 TABLESPACE tbs_02),
    PARTITION q4_2000
      (SUBPARTITION pq4001 TABLESPACE tbs_03, 
       SUBPARTITION pq4002 TABLESPACE tbs_03,
       SUBPARTITION pq4003 TABLESPACE tbs_03,
       SUBPARTITION pq4004 TABLESPACE tbs_03)
);

Bitmap Index Examples

The following creates a bitmap index on the table oe.hash_products, which was created in "Hash Partitioning Example":

CREATE BITMAP INDEX product_bm_ix 
   ON hash_products(list_price)
   TABLESPACE tbs_1
   LOCAL(PARTITION ix_p1 TABLESPACE tbs_02,
         PARTITION ix_p2,
         PARTITION ix_p3 TABLESPACE tbs_03,
         PARTITION ix_p4,
         PARTITION ix_p5 TABLESPACE tbs_04 );

Because hash_products is a partitioned table, the bitmap join index must be locally partitioned. In this example, the user must have quota on tablespaces specified. See CREATE TABLESPACE for examples that create tablespaces tbs_2, tbs_3, and tbs_4.

The next series of statements shows how one might create a bitmap join index on a fact table using a join with a dimension table.

CREATE TABLE hash_products
    ( product_id          NUMBER(6)
    , product_name        VARCHAR2(50)
    , product_description VARCHAR2(2000)
    , category_id         NUMBER(2)
    , weight_class        NUMBER(1)
    , warranty_period     INTERVAL YEAR TO MONTH
    , supplier_id         NUMBER(6)
    , product_status      VARCHAR2(20)
    , list_price          NUMBER(8,2)
    , min_price           NUMBER(8,2)
    , catalog_url         VARCHAR2(50)
    , CONSTRAINT          pk_product_id PRIMARY KEY (product_id)
    , CONSTRAINT          product_status_lov_demo
                          CHECK (product_status in ('orderable'
                                                  ,'planned'
                                                  ,'under development'
                                                  ,'obsolete')
 ) )
 PARTITION BY HASH (product_id)
 PARTITIONS 5
 STORE IN (example); 
 
CREATE TABLE sales_quota
    ( product_id          NUMBER(6)
    , customer_name       VARCHAR2(50)  
    , order_qty           NUMBER(6)
  ,CONSTRAINT u_product_id UNIQUE(product_id)
 ); 
 
CREATE BITMAP INDEX product_bm_ix
   ON hash_products(list_price)
   FROM hash_products h, sales_quota s
   WHERE h.product_id = s.product_id
   TABLESPACE example
   LOCAL(PARTITION ix_p1 TABLESPACE example,
         PARTITION ix_p2,
         PARTITION ix_p3 TABLESPACE example,
         PARTITION ix_p4,
         PARTITION ix_p5 TABLESPACE example ); 

Indexes on Nested Tables: Example

The sample table pm.print_media contains a nested table column ad_textdocs_ntab, which is stored in storage table textdocs_nestedtab. The following example creates a unique index on storage table textdocs_nestedtab:

CREATE UNIQUE INDEX nested_tab_ix
      ON textdocs_nestedtab(NESTED_TABLE_ID, document_typ);

Including pseudocolumn NESTED_TABLE_ID ensures distinct rows in nested table column ad_textdocs_ntab.

Indexing on Substitutable Columns: Examples

You can build an index on attributes of the declared type of a substitutable column. In addition, you can reference the subtype attributes by using the appropriate TREAT function. The following example uses the table books, which is created in "Substitutable Table and Column Examples". The statement creates an index on the salary attribute of all employee authors in the books table:

CREATE INDEX salary_i 
   ON books (TREAT(author AS employee_t).salary);

The target type in the argument of the TREAT function must be the type that added the attribute being referenced. In the example, the target of TREAT is employee_t, which is the type that added the salary attribute.

If this condition is not satisfied, then Oracle Database interprets the TREAT function as any functional expression and creates the index as a function-based index. For example, the following statement creates a function-based index on the salary attribute of part-time employees, assigning nulls to instances of all other types in the type hierarchy.

CREATE INDEX salary_func_i ON persons p
   (TREAT(VALUE(p) AS part_time_emp_t).salary);

You can also build an index on the type-discriminant column underlying a substitutable column by using the SYS_TYPEID function.

Note:

Oracle Database uses the type-discriminant column to evaluate queries that involve the IS OF type condition. The cardinality of the typeid column is normally low, so Oracle recommends that you build a bitmap index in this situation.

The following statement creates a bitmap index on the typeid of the author column of the books table:

CREATE BITMAP INDEX typeid_i ON books (SYS_TYPEID(author));

See Also: