mysql - 如何重写查询替换(或)，(和)条件

Question

1. 查询执行时间太长，大约需要 130 分钟。
2. 表具有索引，但查询未使用索引。
3. 表大小约为 3000 万条记录。
4. 请帮助我通过更改(或)、(和)条件来重写查询。
5. 该查询未在正常执行中使用，因此我们尝试使用强制索引，但没有成功。

查询:

SELECT customer_history.customer_id,
        customer_history.row_mod,
        customer_history.row_create,
        customer_history.event_id,
        customer_history.event_type,
        customer_history.new_value,
        customer_history.old_value
FROM customer_history FORCE INDEX (customer_history_n2)
WHERE customer_id >= 1
        AND customer_id < 5000000
        AND (customer_history.row_mod >= '2012-10-01')
        OR (
                customer_history.row_create >= '2012-10-01'
                AND customer_history.row_create < '2012-10-13'
                );


Table structure

    CREATE TABLE `customer_history` (
      `customer_id` int(11) NOT NULL,
      `row_mod` datetime DEFAULT NULL,
      `row_create` datetime DEFAULT NULL,
      `event_id` int(11) DEFAULT NULL,
      `event_type` varchar(45) DEFAULT NULL,
      `new_value` varchar(255) DEFAULT NULL,
      `old_value` varchar(255) DEFAULT NULL,
      KEY `customer_id1` (`customer_id`),
      KEY `new_value_n1` (`new_value`),
      KEY `customer_history_n1` (`row_create`),
      KEY `customer_history_n2` (`row_mod`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8

解释计划:

+----+-------------+------------------+------+---------------------+------+---------+------+----------+-------------+
| id | select_type | table            | type | possible_keys       | key  | key_len | ref  | rows     | Extra       |
+----+-------------+------------------+------+---------------------+------+---------+------+----------+-------------+
|  1 | SIMPLE      | customer_history | ALL  | customer_history_n2 | NULL | NULL    | NULL | 18490530 | Using where |
+----+-------------+------------------+------+---------------------+------+---------+------+----------+-------------+
1 row in set (0

Answer 1

您可以尝试将此查询分成两部分:

SELECT customer_history.customer_id,
        customer_history.row_mod,
        customer_history.row_create,
        customer_history.event_id,
        customer_history.event_type,
        customer_history.new_value,
        customer_history.old_value
FROM customer_history
WHERE customer_id >= 1
        AND customer_id < 5000000
        AND (customer_history.row_mod >= '2012-10-01')

和

SELECT customer_history.customer_id,
        customer_history.row_mod,
        customer_history.row_create,
        customer_history.event_id,
        customer_history.event_type,
        customer_history.new_value,
        customer_history.old_value
FROM customer_history
WHERE  customer_history.row_create >= '2012-10-01'
       AND customer_history.row_create < '2012-10-13';

并查看其中哪一个需要更长的时间来执行和优化它们。为了获得与第一个查询相同的结果集，您可以在 MySQL 中UNION这两个查询，或者简单地从应用程序层单独执行它们并在那里连接结果集。