Apr 272011
Explain query execution plan in MySQL
Answer:
To get a better understanding of the performance of your MySQL query, you can use the explain statement.
E.g.
mysql> explain select * from user where host = 'localhost';
+----+-------------+-------+------+---------------+---------+---------+-------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+------+---------------+---------+---------+-------+------+-------------+
| 1 | SIMPLE | user | ref | PRIMARY | PRIMARY | 180 | const | 12 | Using where |
+----+-------------+-------+------+---------------+---------+---------+-------+------+-------------+Usually you need to look at the column "key" to see if index was being used, and the column "rows" to see how many rows are scanned for the query.
