Learn more about how to delete indexes in MYSQL

MYSQL is a relational database management system, and indexes are a very important part of MYSQL. In MYSQL, the index can quickly locate a record location, thereby improving query efficiency. But when indexes expire or are no longer used, we need to delete them to reduce the burden on the database. In this article, we will take an in-depth look at how to delete indexes in MYSQL.

1. Basic knowledge of indexes

1. What is an index
The index is a data structure used to speed up data retrieval in MYSQL. It is an independent data object consisting of one or more columns. In order to speed up query efficiency, the index will arrange the data in the table according to certain rules and record the location of each data row. When querying, MYSQL will use the index to locate the target data row, thereby improving query efficiency.

2. Classification of indexes
In MYSQL, indexes are mainly divided into two categories: clustered indexes and non-clustered indexes. A clustered index means that the physical order of data rows is consistent with the logical order of key values. Each table can only have one clustered index. Non-clustered indexes are logically unordered, and a table can contain multiple non-clustered indexes.

In addition, indexes can also be classified according to different storage mechanisms. HASH index, B-TREE index, and FULLTEXT index are all indexes with different storage mechanisms.

2. Delete the index

In MYSQL, you can use the "DROP INDEX" command or the "ALTER TABLE" command to delete the index.

1. DROP INDEX command
The DROP INDEX command can directly delete the index with the specified name. The command format is as follows:

DROP INDEX index_name ON table_name

Among them, index_name is the name of the index that needs to be deleted, and table_name is the name of the corresponding table. After executing the command, MYSQL will delete the corresponding index.

For example: We now need to delete the index named index_name in the table student, then we can execute the following command:

DROP INDEX index_name ON student

2, ALTER TABLE command
ALTER TABLE command can modify the table structure, one of the operations is to delete an index. The command format is as follows:

ALTER TABLE table_name DROP INDEX index_name

Among them, table_name is the name of the table to be operated on, and index_name is the name of the index that needs to be deleted. After executing the command, MYSQL will delete the corresponding index in the table.

For example: We now need to delete the index named index_name in the table student, then we can execute the following command:

ALTER TABLE student DROP INDEX index_name

3. Notes

1. Delete index requirements Be careful
Indexes are a very important part of MYSQL. Deleting wrong or unnecessary indexes will lead to reduced query efficiency or other problems. Therefore, before deleting the index, we must fully analyze and judge the index to confirm that the index to be deleted is indeed no longer used or has expired.

2. Deleting an index must follow the specifications
Deleting an index in MYSQL must follow the relevant specifications, and pay attention to the command format, execution steps, etc. Any irregular operation may cause serious errors and problems.

4. Summary

Index is a very important part of MYSQL, which can speed up query efficiency and improve database performance. However, during use, index expiration and uselessness often occur. Therefore, we need to know how to delete indexes and precautions to avoid performance degradation and other problems caused by index problems.

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