Mysql 如何按顺序从三个或更多相关表中选择值
我的数据库中有三个相关的表<代码>语法，Mysql 如何按顺序从三个或更多相关表中选择值,mysql,sql,Mysql,Sql,我的数据库中有三个相关的表语法，用户和组织。 语法表格通过字段creator与用户表格相关，字段类型为int，是来自用户id的外键。 接下来是组织表，该表依次与用户表相关Userstable字段organization是表organizations id的外键。 例如，我如何通过id选择语法，然后选择其相应的创建者信息，然后选择用户所属的相应的组织信息 描述语法 +------------------+------------------+------+-----+---------+-----
用户组织语法creator用户int用户id组织用户idorganizationorganizations idid创建者组织描述语法
+------------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------------+------------------+------+-----+---------+----------------+
| id | int(11) unsigned | NO | PRI | NULL | auto_increment |
| name | varchar(255) | NO | | NULL | |
| short_name | varchar(255) | YES | | NULL | |
| description | varchar(255) | YES | | NULL | |
| domain | int(10) unsigned | YES | MUL | NULL | |
| url | varchar(255) | YES | | NULL | |
| seo_friendly_url | varchar(255) | NO | | NULL | |
| encoding | int(11) unsigned | YES | MUL | NULL | |
| distribution | int(11) unsigned | YES | MUL | NULL | |
| project | int(11) unsigned | YES | MUL | NULL | |
| creator | int(11) unsigned | YES | MUL | NULL | |
| language | int(11) unsigned | YES | MUL | NULL | |
| link | varchar(255) | NO | | NULL | |
| creation_date | datetime | NO | | NULL | |
| last_update | datetime | NO | | NULL | |
| schema | varchar(255) | YES | | NULL | |
| type | int(11) unsigned | YES | MUL | NULL | |
| organization | int(11) unsigned | YES | MUL | NULL | |
+------------------+------------------+------+-----+---------+----------------+
+--------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+------------------+------+-----+---------+----------------+
| id | int(11) unsigned | NO | PRI | NULL | auto_increment |
| first_name | varchar(20) | NO | | NULL | |
| last_name | varchar(40) | NO | | NULL | |
| username | varchar(30) | NO | MUL | NULL | |
| password | varbinary(32) | NO | | NULL | |
| email | varchar(80) | NO | MUL | NULL | |
| organization | int(11) unsigned | YES | MUL | NULL | |
| group | int(11) unsigned | NO | MUL | 1 | |
+--------------+------------------+------+-----+---------+----------------+
描述用户
+------------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------------+------------------+------+-----+---------+----------------+
| id | int(11) unsigned | NO | PRI | NULL | auto_increment |
| name | varchar(255) | NO | | NULL | |
| short_name | varchar(255) | YES | | NULL | |
| description | varchar(255) | YES | | NULL | |
| domain | int(10) unsigned | YES | MUL | NULL | |
| url | varchar(255) | YES | | NULL | |
| seo_friendly_url | varchar(255) | NO | | NULL | |
| encoding | int(11) unsigned | YES | MUL | NULL | |
| distribution | int(11) unsigned | YES | MUL | NULL | |
| project | int(11) unsigned | YES | MUL | NULL | |
| creator | int(11) unsigned | YES | MUL | NULL | |
| language | int(11) unsigned | YES | MUL | NULL | |
| link | varchar(255) | NO | | NULL | |
| creation_date | datetime | NO | | NULL | |
| last_update | datetime | NO | | NULL | |
| schema | varchar(255) | YES | | NULL | |
| type | int(11) unsigned | YES | MUL | NULL | |
| organization | int(11) unsigned | YES | MUL | NULL | |
+------------------+------------------+------+-----+---------+----------------+
+--------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+------------------+------+-----+---------+----------------+
| id | int(11) unsigned | NO | PRI | NULL | auto_increment |
| first_name | varchar(20) | NO | | NULL | |
| last_name | varchar(40) | NO | | NULL | |
| username | varchar(30) | NO | MUL | NULL | |
| password | varbinary(32) | NO | | NULL | |
| email | varchar(80) | NO | MUL | NULL | |
| organization | int(11) unsigned | YES | MUL | NULL | |
| group | int(11) unsigned | NO | MUL | 1 | |
+--------------+------------------+------+-----+---------+----------------+
描述组织
+--------------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------------+------------------+------+-----+---------+----------------+
| id | int(11) unsigned | NO | PRI | NULL | auto_increment |
| name | varchar(255) | NO | | NULL | |
| department | varchar(255) | NO | | NULL | |
| communication_info | varchar(255) | NO | | NULL | |
+--------------------+------------------+------+-----+---------+----------------+
当我尝试
SELECT Grammars.name AS name, Grammars.description AS description,
Domains.name AS domain,Types.name AS type, Languages.name AS language,
Encodings.name AS encoding,
Organizations.name AS organization_name, Organizations.department AS organization_department, Organizations.communication_info AS organization_comm_info,
Users.last_name AS creator_last_name, Users.first_name AS creator_first_name, Users.email AS creator_email,
Projects.name AS project_name, Projects.short_name AS project_short_name, Projects.url AS project_url,
Projects.funding AS project_funding, Projects.funder AS project_funder,
Projects.start_date AS project_start_date, Projects.end_date AS project_end_date
FROM Grammars
LEFT JOIN Domains ON Grammars.domain=Domains.id
LEFT JOIN Types ON Grammars.type=Types.id
LEFT JOIN Languages ON Grammars.language=Languages.id
LEFT JOIN Projects ON Grammars.project = Projects.id
LEFT JOIN Encodings ON Grammars.encoding = Encodings.id
LEFT JOIN Users ON Grammars.creator = Users.id
LEFT JOIN Organizations ON Users.organization = Organizations.id
WHERE Grammars.id = 3 ;
当有值时，我得到空集。任何建议？？？此查询不返回任何数据的唯一原因是因为语法中没有可以完成以下任务的行：
Grammars.id=id
如果您使用的是LEFT JOIN，它将不会限制语法返回。
“id”的值是多少？查看表的描述，我发现每个表中都有一个“id”字段。。。您应该限定此字段名，并确保某些行满足条件。这是哪个id“WHERE Grammars.id=id；”？您希望记录的顺序是水平的还是垂直的？您声明数据库中有3个表，但要连接3个以上的表，您是否有其他表，如域
，类型`，等等？是的，我当然没有插入他们的描述，因为在我在查询中插入用户和组织之间的最后一个联接之前，查询工作正常。这是一个存储过程，这就是为什么您会看到id。我用id=3调用它，但仍然没有得到任何结果（空集）。并且在id=3的语法中存在一行？