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- CREATE TABLE `object_items` (
- `item_name` varchar(50) NOT NULL DEFAULT '',
- `object_id` int(10) unsigned NOT NULL DEFAULT '0',
- `sequence` int(10) unsigned NOT NULL,
- `completed` tinyint(1) NOT NULL DEFAULT '0',
- `is_active` tinyint(1) NOT NULL DEFAULT '0',
- `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
- PRIMARY KEY (`id`),
- UNIQUE KEY `uni_seq_object_id` (`sequence`,`object_id`),
- KEY `idx_object_id` (`object_id`),
- KEY `idx_seq` (`sequence`)
- ) ENGINE=InnoDB AUTO_INCREMENT=3408237 DEFAULT CHARSET=utf8mb4
- +-----------+-----------+----------+-----------+------+
- | item_name | object_id | sequence | completed | id |
- +-----------+-----------+----------+-----------+------+
- | ABCD | 10 | 1 | 1 | 1 |
- | BCDE | 10 | 2 | 1 | 2 |
- | CDEF | 10 | 3 | 1 | 3 |
- | DEFG | 10 | 4 | 0 | 4 |
- | ABCD | 11 | 1 | 1 | 5 |
- | BCDE | 11 | 2 | 1 | 6 |
- | CDEF | 11 | 3 | 0 | 7 |
- | DEFG | 11 | 4 | 0 | 8 |
- | ABCD | 12 | 1 | 1 | 9 |
- | BCDE | 12 | 2 | 1 | 10 |
- +-----------+-----------+----------+-----------+------+
- +-----------+-----------+----------+-----------+------+
- | item_name | object_id | sequence | completed | id |
- +-----------+-----------+----------+-----------+------+
- | DEFG | 10 | 4 | 0 | 4 |
- | CDEF | 11 | 3 | 0 | 7 |
- +-----------+-----------+----------+-----------+------+
- select
- a.*
- from object_items a
- where a.sequence = (
- select min(sequence)
- from object_items b
- where a.object_id = b.object_id
- and b.completed = 0
- )
- +----+--------------------+-------+------------+------+---------------+---------------+---------+-----------------+---------+----------+-------------+
- | id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
- +----+--------------------+-------+------------+------+---------------+---------------+---------+-----------------+---------+----------+-------------+
- | 1 | PRIMARY | a | NULL | ALL | NULL | NULL | NULL | NULL | 3268598 | 100.00 | Using where |
- | 2 | DEPENDENT SUBQUERY | b | NULL | ref | idx_object_id | idx_object_id | 4 | db.a.object_id | 21 | 10.00 | Using where |
- +----+--------------------+-------+------------+------+---------------+---------------+---------+-----------------+---------+----------+-------------+
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