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| Тема |
 Re: Теоретично [re: TPECKATA] |
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| Автор |
bal-bal (непознат
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| Публикувано | 30.03.07 21:14 |
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има ли разлика между left_join i select s1,s2,s3 from t1,t2,t3
koe e po dobre da polzvam
mysql> explain select userid,payment_code from users,payments where vip = 1 and userid = user_id and payment_type = 'vip';
+----+-------------+----------+--------+---------------+---------+---------+-------------------------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------+--------+---------------+---------+---------+-------------------------+------+-------------+
| 1 | SIMPLE | payments | ALL | user_id | NULL | NULL | NULL | 2287 | Using where |
| 1 | SIMPLE | users | eq_ref | PRIMARY | PRIMARY | 3 | bgfree.payments.user_id | 1 | Using where |
+----+-------------+----------+--------+---------------+---------+---------+-------------------------+------+-------------+
2 rows in set (0.01 sec)
mysql> explain select userid,payment_code from users left join payments on (userid = user_id) where vip = 1 and payment_type = 'vip';
+----+-------------+----------+--------+---------------+---------+---------+-------------------------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------+--------+---------------+---------+---------+-------------------------+------+-------------+
| 1 | SIMPLE | payments | ALL | user_id | NULL | NULL | NULL | 2287 | Using where |
| 1 | SIMPLE | users | eq_ref | PRIMARY | PRIMARY | 3 | bgfree.payments.user_id | 1 | Using where |
+----+-------------+----------+--------+---------------+---------+---------+-------------------------+------+-------------+
2 rows in set (0.00 sec)
mysql>
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