The above syntax is used to create the index with specific function in oracle which will be user-defined function or any built in oracle function.These functional based indexes will be useful for improving the performance of the queries where user is using different functions. You can override this storage by specifying different tablespace storage for the subpartitions of an individual partition in the second STORE IN clause in the index_subpartition_clause. Restriction on Index Physical Attributes You cannot specify the PCTUSED parameter for an index. To create an index in your own schema, one of the following conditions must be true: The table or cluster to be indexed must be in your own schema. 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. The query must be guaranteed not to need any NULL values from the indexed expression, since NULL values are not stored in indexes. logging_clause Specify whether the creation of the index will be logged (LOGGING) or not logged (NOLOGGING) in the redo log file. key_compression Specify COMPRESS to enable key compression, which eliminates repeated occurrence of key column values and may substantially reduce storage. This is the default. 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. The following example creates a unique index on storage table textdocs_nestedtab: Including pseudocolumn NESTED_TABLE_ID ensures distinct rows in nested table column ad_textdocs_ntab. Non-unique indexes do not impose this restriction on the column values. For nonunique indexes, the valid range of prefix length values is from 1 to the number of key columns. If the name conflicts with an existing index subpartition name, then the database uses the form SYS_SUBPn. Create the following partitioned table. See CREATE TABLESPACE for examples that create tablespaces tbs_1 and tbs_2. Additionally, to use a function-based index: The table must be analyzed after the index is created. The only property you can specify for hash partitions is tablespace storage. The sample table pm.print_media contains a nested table column ad_textdocs_ntab, which is stored in storage table textdocs_nestedtab. Oracle indexes - create, rebuild, select, drop. That is, 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). They enable you to construct queries that evaluate the value returned by an expression, which in turn may include built-in or user-defined functions. The following example creates a unique index: Alternatively, you can define UNIQUE integrity constraints on the desired columns. You can build an index on attributes of the declared type of a substitutable column. You cannot reverse a bitmap index or an index on an index-organized table. Use the CREATE UNIQUE INDEX statement to create a unique index. The following statements illustrate online index build operations: Function-based indexes facilitate queries that qualify a value returned by a function or expression. The storage of partitioned database entities in tablespaces of different block sizes is subject to several restrictions. 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. Any rows where all the keys are NULL if table is index-organized, this default is overridden for the to... 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