A picture to understand MySQL explain

Summary description:

1. id: select identifier
2. select_type: indicates the type of query.
3. table: the table of the output result set
4. partitions: matching partitions
5. type: indicates the connection type of the table
6. possible_keys: indicates the index that may be used when querying
7. key: indicates the actual index used
8. key_len: the length of the index field
9. ref: column and index comparison
10. rows: the number of rows scanned (estimated number of rows)
11. filtered: Percentage of rows filtered by table conditions
12. Extra: description and explanation of the implementation

note:

• explain will not tell you information about triggers, stored procedures, or the impact of user-defined functions on queries.
• explain does not consider various caches.
• explain cannot display the optimization work that MySQL has done during query execution.
• Some statistics are estimates.
Yes , it is not an exact value. • explain can only explain SELECT operations, and other operations should be rewritten as SELECT and then view the execution plan.

Original: A picture to thoroughly understand MySQL's explain