What is mysql index file

MySQL index file is a data structure used to quickly find and retrieve data in the database. It is created on one or more columns in the table to improve query performance and data retrieval speed. It contains the index. The key values ​​and pointers to the actual data locations, index files are usually stored on disk, separately from the table data files.

Operating system for this tutorial: Windows 10 system, MySQL 8 version, Dell G3 computer.

MySQL index file is a data structure used to quickly find and retrieve data in the database. It is created on one or more columns in a table to improve query performance and data retrieval speed. The index file contains the index key values ​​and pointers to the actual data locations.

When executing a query in MySQL, if there are no appropriate indexes, the database engine will scan the entire table to find data that meets the query conditions. After using the index, the database engine can directly skip most of the data rows based on the information in the index file and only retrieve relevant data, thereby improving query efficiency.

Index files are usually stored on disk, separately from the table data files, but there are also cases where indexes are stored in memory to further improve query speed.

MySQL supports multiple types of indexes, such as B-tree indexes, hash indexes, full-text indexes, etc. Among them, B-tree index is the most common and important index type. B-tree indexes use a balanced tree data structure, which can maintain the orderliness of the index and enable efficient range queries.

In MySQL, you can use the CREATE INDEX statement to create an index on one or more columns of a table. For example, the following is an example of creating an index named idx_username on a table named users:

CREATE INDEX idx_username ON users (username);

Using indexes can speed up queries, but also increases the cost of data insertion and updates. Therefore, when creating an index, you need to weigh the usage scenarios of the index, the frequency of queries, and the frequency of data operations.

In summary, the MySQL index file is a data structure created to speed up queries. It contains index key values ​​and pointers to actual data locations, which can improve database query performance.

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