为什么空格会影响 MySQL Left Join 并返回 NULL 值？

发布于 2024-12-23 07:37:42 字数 13912 浏览 2 评论 0原文

我遇到了一个奇怪的问题，需要一些帮助来确定原因。到目前为止，我只能观察症状。它“似乎”正在发生的是，MySQL 根据我在第一个“LEFT JOIN”之前是否有换行符来执行不同的查询。

这是我的设置：

我正在 www.xeround.com 提供的 MySQL 数据库实例上运行查询。我正在使用 Kohana 框架，版本 3.0。我在 Lighttpd 上运行 PHP 5.3.3 FastCGI。我使用 MySQL 本机驱动程序编译了 PHP：

--with-mysql=mysqlnd --with-mysqli=mysqlnd --with-pdo-mysql=mysqlnd

我使用默认的 Kohana 3 MySQL 数据库驱动程序和 QueryBuilder。

我将跳过 PHP 代码并共享 SQL，因为这似乎是问题所在。 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：（我删除了从 Fieldreps 表返回的大部分字段，以使其简短且不那么个人化。）

但是，当我在第一个 LEFT JOIN 之前插入换行符时，像这样：

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：

请注意，Users 表上的 LEFT JOIN 在这两种情况下都可以正常工作。我还尝试在第二个 LEFT JOIN 之前添加换行符，而不是第一个。同样不想要的结果。我能找到的唯一解决办法是在第一个 LEFT JOIN 前面放置一个换行符。由 QueryBuilder 构建并发送到 MySQL 的查询始终是长的、单行、最小空白字符串...没有换行符！这是我第一次遇到这个问题。我简直不敢相信需要在第一个 LEFT JOIN 之前放置换行符。

我的问题归结为以下几点：

这应该是这样发生的吗？（空格影响查询结果）
获得我想要的结果的最佳方法是什么。

我不是 SQL 专家，否则我可能不需要问这个问题。我确信有一些事情我忽略了。

谢谢你，

乔纳森

原文

I am having an odd issue and need some help determining the cause. So far, I have only been able to observe the symptoms. What it "seems" is happening is that MySQL is executing the query different based on whether or not I have a newline character before my first "LEFT JOIN".

Here is my setup:

I am running queries on a MySQL Database instance provided by www.xeround.com. I am using the Kohana framework, version 3.0. I am running PHP 5.3.3 FastCGI on Lighttpd. I compiled PHP with the MySQL Native Driver:

--with-mysql=mysqlnd --with-mysqli=mysqlnd --with-pdo-mysql=mysqlnd

I am using the default Kohana 3 MySQL Database Driver and QueryBuilder.

I am going to skip the PHP code and share the SQL since that seems to be the issue. The QueryBuilder ends up building this query:

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`)

Which returns a result like this:(I removed most of the fields returned from the Fieldreps table to keep it short and less personal.)

However, when I insert a newline character immediately before the first LEFT JOIN, like this:

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`)

I now get the result I want:

Notice that the LEFT JOIN on the Users table works fine in both scenarios. I also tried adding the newline before the second LEFT JOIN, instead of the first. Same unwanted result. The only thing that I can find to fix it is placing a newline in front of the first LEFT JOIN. The queries that are built by QueryBuilder and sent to MySQL are always long, single-line, minimum whitespace strings...no newlines! This is the first time I have had this issue. I just can't believe there would be a requirement to place a newline before the first LEFT JOIN.

My question boils down to these points: