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copied!<p>They are the same.</p> <p><strong>Edit</strong>: They are the same in MySQL.</p> <p><em>using an index:</em></p> <pre><code>mysql> explain select * from trees where id = 1 or id = 2; +----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+ | 1 | SIMPLE | trees | range | PRIMARY | PRIMARY | 8 | NULL | 2 | Using where | +----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+ mysql> explain select * from trees where id in (1,2); +----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+ | 1 | SIMPLE | trees | range | PRIMARY | PRIMARY | 8 | NULL | 2 | Using where | +----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+ </code></pre> <p><em>using a full table scan:</em></p> <pre><code>mysql> explain select * from trees where version = 1 or version = 2; +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | trees | ALL | NULL | NULL | NULL | NULL | 7 | Using where | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ mysql> explain select * from trees where version in (1,2); +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | trees | ALL | NULL | NULL | NULL | NULL | 7 | Using where | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ </code></pre>

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