在使用MySQL進行查詢優化的時候，常常需要生成執行計劃文件進行分析和優化。下面介紹一下如何利用MySQL來生成執行計劃文件。

1. 打開MySQL客戶端，并連接到相應的數據庫。

$ mysql -h localhost -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 14
Server version: 5.7.20-0ubuntu0.16.04.1 (Ubuntu)
mysql>

2. 運行使用EXPLAIN關鍵字的SQL查詢語句。

mysql>EXPLAIN SELECT * FROM employees WHERE salary >50000;

3. 查看執行計劃文件。

mysql>SHOW WARNINGS;
+---------+------+-----------------------------------------------------+
| Level   | Code | Message                                             |
+---------+------+-----------------------------------------------------+
| Warning | 1681 | 'NO_INDEX_USED' is deprecated and will be removed in |
|         |      | a future release. Please use 'NO_INDEX' instead     |
| Warning | 1681 | 'NO_INDEX_USED' is deprecated and will be removed in |
|         |      | a future release. Please use 'NO_INDEX' instead     |
+---------+------+-----------------------------------------------------+
mysql>SHOW EXPLAIN;
+----+-------------+-----------+------+---------------+------+---------+------+------+----------+-------------+
| id | select_type | table     | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra       |
+----+-------------+-----------+------+---------------+------+---------+------+------+----------+-------------+
|  1 | SIMPLE      | employees | ALL  | NULL          | NULL | NULL    | NULL |    18 |   100.00 | Using where |
+----+-------------+-----------+------+---------------+------+---------+------+------+----------+-------------+

4. 將執行計劃文件輸出到文件中。

mysql>EXPLAIN SELECT * FROM employees WHERE salary >50000\G >/tmp/plan_file.txt

5. 查看輸出的執行計劃文件。

$ cat /tmp/plan_file.txt
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: employees
partitions: NULL
type: ALL
possible_keys: NULL
key: NULL
key_len: NULL
ref: NULL
rows: 18
filtered: 100.00
Extra: Using where
1 row in set, 1 warning (0.00 sec)

通過上述步驟，我們就可以很方便地生成MySQL的執行計劃文件。這對于進行查詢優化以及性能分析非常有幫助。