Create Index

The following information applies to an index, which is a database 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, as explained in Indexes.

Schema: Database schema that owns the table associated with the index.

Table: Name of the table associated with the index.

Name: Name of the index. Must be unique within a schema.

Index Type: Normal for a standard Oracle index, in which case you also specify non-unique, unique, or bitmap, as well as one or more index expressions; or Text for an Oracle Text index (created with INDEXTYPE IS CTXSYS.CONTEXT), in which case you specify the column to be indexed.

Non-unique means that the index can contain multiple identical values; Unique means that no duplicate values are permitted; Bitmap stores rowids associated with a key value as a bitmap.

Index: A list of index expressions, that is, the table columns or column expressions in the index. To add an index expression, click the Add Column Expression (+) icon; this adds a column name here and in Column Expression, where you can edit it. To delete an index expression, click the Remove Column Expression (X) icon; to move an index expression up or down in the list click the Move Column Up and Move Column Down icons. An index must have at least one index expression.

For example, to create an index on the AUTHOR_LAST_NAME column of the Books table from the tutorial (see Creating a Table (Books)), click the + icon, and select AUTHOR_LAST_NAME in Column Name or Expression (next field), which changes BOOKS to AUTHOR_LAST_NAME in the Index field.

Column Name or Expression: A column name or column expression. A column expression is an expression built from columns, constants, SQL functions, and user-defined functions. When you specify a column expression, you create a function-based index.

Order: ASC for an ascending index (index values sorted in ascending order); DESC for a descending index (index values sorted in descending order).