OR ---- ------------- ---------------- ------- -------------------- --

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OR
+----+-------------+----------------+-------+----------------------------------------------------------------------+------------------------------+---------+-------+------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------------+-------+----------------------------------------------------------------------+------------------------------+---------+-------+------+----------------------------------------------+
| 1 | SIMPLE | zipcodes | range | index_zipcodes_on_url_friendly_city_name,index_zipcodes_on_city_name | index_zipcodes_on_city_name | 33 | NULL | 54 | Using where; Using temporary |
| 1 | SIMPLE | abstract_users | ref | index_abstract_users_on_type,index_abstract_users_on_city | index_abstract_users_on_type | 2 | const | 9619 | Using index condition; Using where; Distinct |
+----+-------------+----------------+-------+----------------------------------------------------------------------+------------------------------+---------+-------+------+----------------------------------------------+
Без OR
+----+-------------+----------------+-------+-----------------------------------------------------------+------------------------------+---------+--------------------------------------+------+------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------------+-------+-----------------------------------------------------------+------------------------------+---------+--------------------------------------+------+------------------------------+
| 1 | SIMPLE | zipcodes | range | index_zipcodes_on_city_name | index_zipcodes_on_city_name | 33 | NULL | 54 | Using where; Using temporary |
| 1 | SIMPLE | abstract_users | ref | index_abstract_users_on_type,index_abstract_users_on_city | index_abstract_users_on_city | 768 | pkwde_development.zipcodes.city_name | 3 | Using where; Distinct |
+----+-------------+----------------+-------+-----------------------------------------------------------+------------------------------+---------+--------------------------------------+------+------------------------------+