MySQL: Explain

id

select_type

table

partitions

type

The type column of EXPLAIN output describes how tables are joined.

possible_keys

key

key_len

長さとは何？

ref

rows

filtered

Extra

Using temporary

Using filesort

MySQL must do an extra pass to find out how to retrieve the rows in sorted order. The sort is done by going through all rows according to the join type and storing the sort key and pointer to the row for all rows that match the WHERE clause. The keys then are sorted and the rows are retrieved in sorted order.

See Section 8.2.1.14, “ORDER BY Optimization”.

Using where

参考