What are the functions of the explain tool in MySQL?

The main functions of the explain tool in MySQL are as follows:

1. Analyze the execution plan of the query: By using the explain tool, you can view MySQL’s execution plan for a given query, including information on the indexes used, connection type, and number of scanned rows. This can help developers optimize query statements and improve query performance.
2. Optimize search queries: The explain tool can display information such as indexes used, connection type, and number of scanned rows during the execution process of a query. By analyzing this information, you can identify performance bottlenecks in the query and then optimize it to improve search efficiency.
3. Check the usage of indexes: The tool can display the indexes used during the execution of a query, by checking the usage of indexes, it can be determined if the indexes are correctly used, and if adjustments or new indexes need to be created.
4. Identifying the performance bottleneck of a query: By analyzing the output of the explain tool, you can determine the performance bottleneck of a query, such as whether there is a full table scan, unnecessary join operations, etc.
5. Understanding the structure and statistics of tables: the Explain tool can display the structure and statistics of tables involved in the execution process of a query, including the number of columns, index situation, table size, etc. This information can help developers better understand the situation of data tables, thus making better optimization decisions.

In general, the explain tool can assist developers in analyzing and optimizing query statements, improving query performance, while also aiding in understanding the database table’s structure and statistical information.