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The EXPLAIN keyword is used throughout various SQL databases and provides information about how your SQL database executes a query. In MySQL, EXPLAIN can be used in front of a query beginning with SELECT , INSERT , DELETE , REPLACE , and UPDATE .
In this manner, what is explain in MySQL?
The EXPLAIN statement provides information about how MySQL executes statements: EXPLAIN works with SELECT , DELETE , INSERT , REPLACE , and UPDATE statements. When EXPLAIN is used with an explainable statement, MySQL displays information from the optimizer about the statement execution plan.
Besides, what is Key_len in MySQL explain?
mysql. According to MySQL website, the key_len column indicates the length of the key that MySQL decided to use. The length is NULL if the key column says NULL . Note that the value of key_len enables you to determine how many parts of a multiple-part key MySQL actually uses.
As described here in the MySQL docs: The filtered column indicates an estimated percentage of table rows that will be filtered by the table condition. That is, rows shows the estimated number of rows examined and rows × filtered / 100 shows the number of rows that will be joined with previous tables. As of MySQL 5.7.