MySQL explain filtered is a command that provides information about how the MySQL optimizer chooses to execute a query. It shows the estimated number of rows that will be examined from the table and helps users to optimize their queries.
The «filtered» column in the output of the explain command indicates the percentage of rows that the optimizer expects to be examined when the query is executed. This value is a rough estimate based on the available statistics about the table.
For example, if the value of «filtered» is 50%, it means that the optimizer expects the query to examine about half of the rows in the table.
This information can be used to optimize the query by adding appropriate indexes or rewriting the query in a more efficient way. By analyzing the output of the explain command, users can make informed decisions about how to improve query performance and avoid slow and inefficient queries.
In conclusion, the MySQL explain filtered command is a powerful tool that helps users to optimize their queries by providing valuable information about how the MySQL optimizer chooses to execute them. Understanding this command and using it effectively can help improve the performance and efficiency of MySQL databases.