What is an index in database?

Answer 1

Oracle includes numerous data structures to improve the speed of Oracle SQL queries. Oracle includes many new indexing algorithms that dramatically increase the speed with which Oracle queries are serviced like b-tree index, bitmap indexes, function-based indexes, and index-only tables (IOTs

Oracle uses indexes to avoid the need for large-table, full-table scans and disk sorts, which are required when the SQL optimizer cannot find an efficient way to service the SQL query. I begin our look at Oracle indexing with a review of standard Oracle b-tree index methodologies.

Answer 2

An index is a performance-tuning method of allowing faster retrieval of records. An index creates an entry for each value that appears in the indexed columns. By default, Oracle creates B-tree indexes

The syntax for creating a index is:

CREATE [UNIQUE] INDEX index_name

ON table_name (column1, column2, . column_n)

[ COMPUTE STATISTICS ];

UNIQUE indicates that the combination of values in the indexed columns must be unique.

COMPUTE STATISTICS tells Oracle to collect statistics during the creation of the index. The statistics are then used by the optimizer to choose a "plan of execution" when SQL statements are executed.

Answer 3

Indexes are required to represent the sequence of stored record occurences within their stored file. There are five types of indexing techniques. 1)Non dense indexing 2) multilevel indexing 3) indexing on field combinations 4) selectivity in the index 5) symbolic pointer representations.

Answer 4

An index in oracle is same as the index in your book. Indexing allows for faster retrieval of data or records . When ever we search for any record ,rather than looking and verifying each record , it can just search it from the index .

Answer 5

Index in oracle is just like the index in a book. It helps for faster data or record retrieval . As it will be a lot easier to search from a index than searching from entire database records .

Answer 6

index is used to increase the speed of query retriveing, when index column is specified in where condition.