moj mysql (4.1.9-max na windowsima) prikaze drugacije:
Kôd:
mysql> alter table master add index category_id(category_id);
Query OK, 177693 rows affected (1.80 sec)
Records: 177693 Duplicates: 0 Warnings: 0
mysql> explain SELECT m.*, c.description FROM master m, categories c WHERE m.category_id = c.category_id;
+----+-------------+-------+--------+---------------+---------+---------+-----------------------+--------+----
---+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Ext
ra |
+----+-------------+-------+--------+---------------+---------+---------+-----------------------+--------+----
---+
| 1 | SIMPLE | m | ALL | category_id | NULL | NULL | NULL | 177693 |
|
| 1 | SIMPLE | c | eq_ref | PRIMARY | PRIMARY | 4 | measure.m.category_id | 1 |
|
+----+-------------+-------+--------+---------------+---------+---------+-----------------------+--------+----
---+
2 rows in set (0.00 sec)
mysql> explain SELECT m.*, c.description FROM master m LEFT JOIN categories c ON m.category_id = c.category_id
;
+----+-------------+-------+--------+---------------+---------+---------+-----------------------+--------+----
---+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Ext
ra |
+----+-------------+-------+--------+---------------+---------+---------+-----------------------+--------+----
---+
| 1 | SIMPLE | m | ALL | NULL | NULL | NULL | NULL | 177693 |
|
| 1 | SIMPLE | c | eq_ref | PRIMARY | PRIMARY | 4 | measure.m.category_id | 1 |
|
+----+-------------+-------+--------+---------------+---------+---------+-----------------------+--------+----
---+
2 rows in set (0.00 sec)
Odnosno gledace sva polja tabele master, i za inner i za left join, bas kao i kad nema indexa.. sto se pokaze i kad se pusti ovaj Pedjin test, jer se dobije skoro isti rezultati...bar sa myisam tabelama, kasno je pa me mrzi da probam innoDB kako se ponasa...