我有一个奇怪的问题，需要一些帮助来确定原因。到目前为止，我只能观察到这些症状。它似乎正在发生的是MySQL在第一次“LEFT JOIN”之前根据我是否有换行符来执行不同的查询。
这是我的设置：
我在www.xeround.com提供的MySQL数据库实例上运行查询。我使用的是Kohana框架3.0版。我在Lighttpd上运行PHP 5.3.3 FastCGI。我使用MySQL Native Driver编译PHP：
- with-mysql = mysqlnd --with-mysqli = mysqlnd --with-pdo-mysql = mysqlnd
我正在使用默认的Kohana 3 MySQL数据库驱动程序和QueryBuilder。
我将跳过PHP代码并共享SQL，因为这似乎是个问题。 QueryBuilder最终构建此查询：
SELECT `fieldreps`.`user_id` AS `fieldreps.user_id`, `fieldreps`.`availability_id` AS `fieldreps.availability_id`, `fieldreps`.`applicant_type` AS `fieldreps.applicant_type`, `fieldreps`.`license_number` AS `fieldreps.license_number`, `fieldreps`.`license_exp` AS `fieldreps.license_exp`, `fieldreps`.`license_state` AS `fieldreps.license_state`, `fieldreps`.`car` AS `fieldreps.car`, `fieldreps`.`authorized_worker` AS `fieldreps.authorized_worker`, `fieldreps`.`restrictions` AS `fieldreps.restrictions`, `fieldreps`.`night` AS `fieldreps.night`, `fieldreps`.`day` AS `fieldreps.day`, `fieldreps`.`longer` AS `fieldreps.longer`, `fieldreps`.`commitment` AS `fieldreps.commitment`, `fieldreps`.`travel_metro` AS `fieldreps.travel_metro`, `fieldreps`.`travel_states` AS `fieldreps.travel_states`, `fieldreps`.`big_employee` AS `fieldreps.big_employee`, `fieldreps`.`employed` AS `fieldreps.employed`, `fieldreps`.`retail` AS `fieldreps.retail`, `fieldreps`.`status` AS `fieldreps.status`, `fieldreps`.`start` AS `fieldreps.start`, `fieldreps`.`sales` AS `fieldreps.sales`, `fieldreps`.`study` AS `fieldreps.study`, `fieldreps`.`relevant` AS `fieldreps.relevant`, `fieldreps`.`experience` AS `fieldreps.experience`, `fieldreps`.`claims` AS `fieldreps.claims`, `fieldreps`.`education` AS `fieldreps.education`, `fieldreps`.`degree_details` AS `fieldreps.degree_details`, `fieldreps`.`degree_institution` AS `fieldreps.degree_institution`, `fieldreps`.`other_training` AS `fieldreps.other_training`, `fieldreps`.`jobs` AS `fieldreps.jobs`, `fieldreps`.`current_training` AS `fieldreps.current_training`, `fieldreps`.`interested` AS `fieldreps.interested`, `fieldreps`.`achievements` AS `fieldreps.achievements`, `fieldreps`.`passions` AS `fieldreps.passions`, `fieldreps`.`ambitions` AS `fieldreps.ambitions`, `fieldreps`.`max_travel_time` AS `fieldreps.max_travel_time`, `fieldreps`.`creation_time` AS `fieldreps.creation_time`, `fieldreps`.`resume` AS `fieldreps.resume`, `users`.`user_id` AS `users.user_id`, `users`.`email` AS `users.email`, `users`.`name` AS `users.name`, `users`.`password` AS `users.password`, `users`.`given_name` AS `users.given_name`, `users`.`title` AS `users.title`, `users`.`nationality` AS `users.nationality`, `availabilities`.`availability_id` AS `availabilities.availability_id`, `availabilities`.`fieldrep_id` AS `availabilities.fieldrep_id`, `availabilities`.`mon_start` AS `availabilities.mon_start`, `availabilities`.`mon_end` AS `availabilities.mon_end`, `availabilities`.`tue_start` AS `availabilities.tue_start`, `availabilities`.`tue_end` AS `availabilities.tue_end`, `availabilities`.`wed_start` AS `availabilities.wed_start`, `availabilities`.`wed_end` AS `availabilities.wed_end`, `availabilities`.`thur_start` AS `availabilities.thur_start`, `availabilities`.`thur_end` AS `availabilities.thur_end`, `availabilities`.`fri_start` AS `availabilities.fri_start`, `availabilities`.`fri_end` AS `availabilities.fri_end`, `availabilities`.`sat_start` AS `availabilities.sat_start`, `availabilities`.`sat_end` AS `availabilities.sat_end`, `availabilities`.`sun_start` AS `availabilities.sun_start`, `availabilities`.`sun_end` AS `availabilities.sun_end` FROM `fieldreps` AS `fieldreps` LEFT JOIN `users` ON (`fieldreps`.`user_id` = `users`.`user_id`) LEFT JOIN `availabilities` ON (`fieldreps`.`availability_id` = `availabilities`.`availability_id`)
返回如下结果:(我删除了Fieldreps表中返回的大部分字段，以保持简短且不太个性化。）
[0] => Array
(
[fieldreps.user_id] => 1f01f4c2-43fd-550d-a53d-1f191786ebad
[fieldreps.availability_id] => e31b0773-ecba-41d1-8ebb-7ac718496456
[fieldreps.car] => Yes
[fieldreps.authorized_worker] => Yes
[fieldreps.restrictions] => Has Restrictions: No
[fieldreps.night] => Yes
[fieldreps.day] => Yes
[fieldreps.longer] => Yes
[users.user_id] => 1f01f4c2-43fd-550d-a53d-1f191786ebad
[users.email] => dsfsdfsdfsdfsdfs@sdfsdfsdfsdfsd.com
[users.name] => Jones
[users.password] =>
[users.given_name] => Fred
[users.title] => Miss
[users.nationality] =>
[availabilities.availability_id] =>
[availabilities.fieldrep_id] =>
[availabilities.mon_start] =>
[availabilities.mon_end] =>
[availabilities.tue_start] =>
[availabilities.tue_end] =>
[availabilities.wed_start] =>
[availabilities.wed_end] =>
[availabilities.thur_start] =>
[availabilities.thur_end] =>
[availabilities.fri_start] =>
[availabilities.fri_end] =>
[availabilities.sat_start] =>
[availabilities.sat_end] =>
[availabilities.sun_start] =>
[availabilities.sun_end] =>
)
[1] => Array
(
[fieldreps.user_id] => 812c3a9f-d7d8-565a-a886-1b182753dd41
[fieldreps.availability_id] =>
[fieldreps.car] => 1
[fieldreps.authorized_worker] => 1
[fieldreps.restrictions] =>
[fieldreps.night] => 1
[fieldreps.day] => 1
[fieldreps.longer] => 1
[users.user_id] => 812c3a9f-d7d8-565a-a886-1b182753dd41
[users.email] => sdfsdfsdfsdfsdf@sdfsdfsdfsdf.com
[users.name] => Smith
[users.password] =>
[users.given_name] => Jill
[users.title] =>
[users.nationality] =>
[availabilities.availability_id] =>
[availabilities.fieldrep_id] =>
[availabilities.mon_start] =>
[availabilities.mon_end] =>
[availabilities.tue_start] =>
[availabilities.tue_end] =>
[availabilities.wed_start] =>
[availabilities.wed_end] =>
[availabilities.thur_start] =>
[availabilities.thur_end] =>
[availabilities.fri_start] =>
[availabilities.fri_end] =>
[availabilities.sat_start] =>
[availabilities.sat_end] =>
[availabilities.sun_start] =>
[availabilities.sun_end] =>
但是，当我在第一个LEFT JOIN之前插入换行符时，如下所示：
SELECT `fieldreps`.`user_id` AS `fieldreps.user_id`, `fieldreps`.`availability_id` AS `fieldreps.availability_id`, `fieldreps`.`applicant_type` AS `fieldreps.applicant_type`, `fieldreps`.`license_number` AS `fieldreps.license_number`, `fieldreps`.`license_exp` AS `fieldreps.license_exp`, `fieldreps`.`license_state` AS `fieldreps.license_state`, `fieldreps`.`car` AS `fieldreps.car`, `fieldreps`.`authorized_worker` AS `fieldreps.authorized_worker`, `fieldreps`.`restrictions` AS `fieldreps.restrictions`, `fieldreps`.`night` AS `fieldreps.night`, `fieldreps`.`day` AS `fieldreps.day`, `fieldreps`.`longer` AS `fieldreps.longer`, `fieldreps`.`commitment` AS `fieldreps.commitment`, `fieldreps`.`travel_metro` AS `fieldreps.travel_metro`, `fieldreps`.`travel_states` AS `fieldreps.travel_states`, `fieldreps`.`big_employee` AS `fieldreps.big_employee`, `fieldreps`.`employed` AS `fieldreps.employed`, `fieldreps`.`retail` AS `fieldreps.retail`, `fieldreps`.`status` AS `fieldreps.status`, `fieldreps`.`start` AS `fieldreps.start`, `fieldreps`.`sales` AS `fieldreps.sales`, `fieldreps`.`study` AS `fieldreps.study`, `fieldreps`.`relevant` AS `fieldreps.relevant`, `fieldreps`.`experience` AS `fieldreps.experience`, `fieldreps`.`claims` AS `fieldreps.claims`, `fieldreps`.`education` AS `fieldreps.education`, `fieldreps`.`degree_details` AS `fieldreps.degree_details`, `fieldreps`.`degree_institution` AS `fieldreps.degree_institution`, `fieldreps`.`other_training` AS `fieldreps.other_training`, `fieldreps`.`jobs` AS `fieldreps.jobs`, `fieldreps`.`current_training` AS `fieldreps.current_training`, `fieldreps`.`interested` AS `fieldreps.interested`, `fieldreps`.`achievements` AS `fieldreps.achievements`, `fieldreps`.`passions` AS `fieldreps.passions`, `fieldreps`.`ambitions` AS `fieldreps.ambitions`, `fieldreps`.`max_travel_time` AS `fieldreps.max_travel_time`, `fieldreps`.`creation_time` AS `fieldreps.creation_time`, `fieldreps`.`resume` AS `fieldreps.resume`, `users`.`user_id` AS `users.user_id`, `users`.`email` AS `users.email`, `users`.`name` AS `users.name`, `users`.`password` AS `users.password`, `users`.`given_name` AS `users.given_name`, `users`.`title` AS `users.title`, `users`.`nationality` AS `users.nationality`, `availabilities`.`availability_id` AS `availabilities.availability_id`, `availabilities`.`fieldrep_id` AS `availabilities.fieldrep_id`, `availabilities`.`mon_start` AS `availabilities.mon_start`, `availabilities`.`mon_end` AS `availabilities.mon_end`, `availabilities`.`tue_start` AS `availabilities.tue_start`, `availabilities`.`tue_end` AS `availabilities.tue_end`, `availabilities`.`wed_start` AS `availabilities.wed_start`, `availabilities`.`wed_end` AS `availabilities.wed_end`, `availabilities`.`thur_start` AS `availabilities.thur_start`, `availabilities`.`thur_end` AS `availabilities.thur_end`, `availabilities`.`fri_start` AS `availabilities.fri_start`, `availabilities`.`fri_end` AS `availabilities.fri_end`, `availabilities`.`sat_start` AS `availabilities.sat_start`, `availabilities`.`sat_end` AS `availabilities.sat_end`, `availabilities`.`sun_start` AS `availabilities.sun_start`, `availabilities`.`sun_end` AS `availabilities.sun_end` FROM `fieldreps` AS `fieldreps`
LEFT JOIN `users` ON (`fieldreps`.`user_id` = `users`.`user_id`) LEFT JOIN `availabilities` ON (`fieldreps`.`availability_id` = `availabilities`.`availability_id`)
我现在得到了我想要的结果：
[0] => Array
(
[fieldreps.user_id] => 1f01f4c2-43fd-550d-a53d-1f191786ebad
[fieldreps.availability_id] => e31b0773-ecba-41d1-8ebb-7ac718496456
[fieldreps.car] => Yes
[fieldreps.authorized_worker] => Yes
[fieldreps.restrictions] => Has Restrictions: No
[fieldreps.night] => Yes
[fieldreps.day] => Yes
[fieldreps.longer] => Yes
[users.user_id] => 1f01f4c2-43fd-550d-a53d-1f191786ebad
[users.email] => dsfsdfsdfsdfsdfs@sdfsdfsdfsdfsd.com
[users.name] => Jones
[users.password] =>
[users.given_name] => Fred
[users.title] => Miss
[users.nationality] =>
[availabilities.availability_id] => e31b0773-ecba-41d1-8ebb-7ac718496456
[availabilities.fieldrep_id] => 1f01f4c2-43fd-550d-a53d-1f191786ebad
[availabilities.mon_start] => 540
[availabilities.mon_end] => 1020
[availabilities.tue_start] => 540
[availabilities.tue_end] => 1020
[availabilities.wed_start] => 540
[availabilities.wed_end] => 1020
[availabilities.thur_start] => 540
[availabilities.thur_end] => 1020
[availabilities.fri_start] => 540
[availabilities.fri_end] => 1020
[availabilities.sat_start] =>
[availabilities.sat_end] =>
[availabilities.sun_start] =>
[availabilities.sun_end] =>
)
[1] => Array
(
[fieldreps.user_id] => 812c3a9f-d7d8-565a-a886-1b182753dd41
[fieldreps.availability_id] =>
[fieldreps.car] => 1
[fieldreps.authorized_worker] => 1
[fieldreps.restrictions] =>
[fieldreps.night] => 1
[fieldreps.day] => 1
[fieldreps.longer] => 1
[users.user_id] => 812c3a9f-d7d8-565a-a886-1b182753dd41
[users.email] => sdfsdfsdfsdfsdf@sdfsdfsdfsdf.com
[users.name] => Smith
[users.password] =>
[users.given_name] => Jill
[users.title] =>
[users.nationality] =>
[availabilities.availability_id] =>
[availabilities.fieldrep_id] =>
[availabilities.mon_start] =>
[availabilities.mon_end] =>
[availabilities.tue_start] =>
[availabilities.tue_end] =>
[availabilities.wed_start] =>
[availabilities.wed_end] =>
[availabilities.thur_start] =>
[availabilities.thur_end] =>
[availabilities.fri_start] =>
[availabilities.fri_end] =>
[availabilities.sat_start] =>
[availabilities.sat_end] =>
[availabilities.sun_start] =>
[availabilities.sun_end] =>
请注意，Users表上的LEFT JOIN在两种情况下都能正常工作。我也尝试在第二个LEFT JOIN之前添加换行符，而不是第一个。同样不需要的结果我唯一可以解决的问题是在第一个LEFT JOIN前放置换行符。由QueryBuilder构建并发送到MySQL的查询总是很长，单行，最小的空白字符串......没有新行！这是我第一次遇到这个问题。我无法相信在第一次LEFT JOIN之前需要设置换行符。
我的问题归结为以下几点：
我不是SQL专家，否则我可能不需要问这个问题。我相信我有一些东西可以忽略。
谢谢，
乔纳森
答案 0 :(得分：0)
我的问题就在我面前，就像我想的那样：
指数
我不经意间在availability.fieldrep_id上创建了两个索引，其余模式的索引充其量只是伪劣。
我使用EXPLAIN表示它没有使用三个连接中的2个的索引。我清理了我的索引，现在每次都很好用。
另外，我想我弄清楚为什么新行会改变查询。如果我一遍又一遍地运行查询，我会看到它在给出的示例之间切换，无论是否添加换行符。我假设MySQL有一些重复查询的缓存。我敢打赌，换行符足以触发它忽略缓存版本，因此它有时会给我所需的结果。
无论如何，问题在于指数。其他一切只是一种症状。
也许这会帮助别人节省一些时间。