MySQL Visual Explain is a command-line tool, not a Graphical User Interface (GUI). You can use it two ways:

    * Give it a query and some connection options, and it will connect and EXPLAIN the query, then show you the result as a tree.
    * Give it the output of EXPLAIN in any of several formats, and it will parse it and turn it into a tree.

Here’s a simple example. Given the following query,

select actor_id,
   (select count(film_id) from sakila.film join sakila.film_actor using(film_id))
from sakila.actor;

You get this EXPLAIN output:

+----+-------------+------------+-------+----------------+--------------------+---------+---------------------+------+-------------+
| id | select_type | table      | type  | possible_keys  | key                | key_len | ref                 | rows | Extra       |
+----+-------------+------------+-------+----------------+--------------------+---------+---------------------+------+-------------+
|  1 | PRIMARY     | actor      | index | NULL           | PRIMARY            | 2       | NULL                |  200 | Using index |
|  2 | SUBQUERY    | film       | index | PRIMARY        | idx_fk_language_id | 1       | NULL                |  951 | Using index |
|  2 | SUBQUERY    | film_actor | ref   | idx_fk_film_id | idx_fk_film_id     | 2       | sakila.film.film_id |    2 | Using index |
+----+-------------+------------+-------+----------------+--------------------+---------+---------------------+------+-------------+

MySQL Visual Explain turns this into the following query execution plan:

SUBQUERY
+- JOIN
|  +- Index lookup
|  |  key            film_actor->idx_fk_film_id
|  |  possible_keys  idx_fk_film_id
|  |  key_len        2
|  |  ref            sakila.film.film_id
|  |  rows           2
|  +- Index scan
|     key            film->idx_fk_language_id
|     possible_keys  PRIMARY
|     key_len        1
|     rows           951
+- Index scan
   key            actor->PRIMARY
   key_len        2
   rows           200

You should read this as a depth-first tree traversal. In other words, the root of the tree is the output node — the last thing that happens in query execution. 

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