为什么whitespace会影响MySQL Left Join并返回NULL值？

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，我只能观察到症状。 “看起来”正在发生的事情是MySQL根据我的第一个“LEFT JOIN”之前是否有换行符执行查询不同。为什么whitespace会影响MySQL Left Join并返回NULL值？

这里是我的设置：

我正在查询由www.xeround.com提供MySQL数据库实例。我正在使用3.0版的Kohana框架。我在Lighttpd上运行PHP 5.3.3 FastCGI。我编译PHP与MySQL的本机驱动程序：

--with-mysql的= mysqlnd --with-的mysqli = mysqlnd --with-PDO MySQL的= mysqlnd

我使用的是默认的Kohana 3个MySQL数据库驱动程序和QueryBuilder。

我打算跳过PHP代码并共享SQL，因为这似乎是问题所在。该QueryBuilder的最终建立这个查询：

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`)

它返回的结果是这样的：（我删除了大部分的领域从Fieldreps表中返回，以保持它短，少个人）

[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] => [email protected] 
     [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] => [email protected] 
     [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] =>

然而，当我第一个离开之前立即插入一个换行符JOIN，类似这样的：

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`)

现在我得到我想要的结果：

[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] => [email protected] 
     [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] => [email protected] 
     [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，在两个方案中，“用户”表上的“左加入”工作正常。我也尝试在第二个LEFT JOIN之前添加换行符，而不是第一个。相同的不需要的结果。我能找到的唯一解决方法是在第一个LEFT JOIN前放置一个换行符。由QueryBuilder构建并发送到MySQL的查询总是很长，单行，最小空白字符串......没有新行！这是我第一次遇到这个问题。我简直不敢相信在第一次LEFT JOIN之前会有要求换行的要求。

我的问题可以归结为以下几点：

难道这是发生这样？（空白影响查询结果）
什么是最好的方式去获得我想要的结果。

我不是SQL专家，否则我可能不需要问这个问题。我确信有一些我可以忽略的东西。

谢谢

乔纳森

来源

2011-12-29 Jonathan

我的问题就在我的面前就像我想：

指数

我无意中在availabilities.fieldrep_id创建了两个指标，以及其余模式的指数最多只能是粗制滥造。

我用EXPLAIN表示它没有使用三个连接中的2个索引。我清理了我的索引，现在每次都能很好地工作。

此外，我想我找出了为什么换行符会改变查询。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有重复查询缓存。我敢打赌，换行足以触发它忽略缓存版本，因此它有时会给我想要的结果。

无论如何，这个问题与索引。其他一切都只是一个症状。

也许这会帮助别人节省一点时间。

来源

2011-12-29 23:18:50 Jonathan

为什么whitespace会影响MySQL Left Join并返回NULL值？

回答

相关问题