Detailed explanation of index types and functions in Oracle database

Detailed explanation of index types and functions in Oracle database

In Oracle database, index is a very important data structure, used to quickly locate and retrieve data. Improve query performance. Indexes can greatly reduce the number of rows in the table that need to be scanned when querying data, thereby speeding up queries. This article will introduce in detail the commonly used index types and their functions in Oracle database, and provide specific code examples.

1. B-Tree index

B-Tree index is one of the most commonly used index types in Oracle database. It stores data in a tree structure, with each node containing multiple child nodes, forming an ordered hierarchical structure. B-Tree index is suitable for equal value query and range query, and can quickly locate the required data.

The sample code to create a B-Tree index is as follows:

CREATE INDEX idx_name ON employees (last_name);

2. Unique index

The unique index is a restriction that the values ​​in the index column cannot Duplicate index. Unique indexes are usually used to ensure unique constraints on a column in a data table. If you try to insert a duplicate index value, Oracle will report an error.

The sample code to create a unique index is as follows:

CREATE UNIQUE INDEX idx_email ON employees (email);

3. Clustered index

Clustered index is to group the data row storage and index of the table An index type that goes together. In a clustered index, data rows are stored in index order, reducing the number of disk I/Os and improving retrieval speed.

The sample code to create a clustered index is as follows:

CREATE CLUSTER idx_dept ON employees (department_id);

4. Full-text index

Full-text index is an index for text type fields and can be used Fuzzy query and full text search. Full-text indexing usually requires the use of a specific full-text search engine to support it.

The sample code to create a full-text index is as follows:

CREATE INDEX idx_description ON products (description) INDEXTYPE IS CTXSYS.CONTEXT;

Summary

Index plays a very important role in Oracle database, which can improve query efficiency and speed up data retrieval. . Different types of indexes are suitable for different scenarios, and developers need to choose the appropriate index type based on specific needs. Through the introduction and code examples of this article, I hope readers can better understand the index types and their functions in the Oracle database.

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