Sql vb.net内部联接3表：附加信息：关键字'；在'；

语法有什么问题。我试图进行

内部联接

3个表，但得到下面的错误消息

其他信息：关键字“on”附近的语法不正确。

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在使用内部联接时，您错过了第2个和第3个表

INNER JOIN <Table 2> on train.class_id = train_class.id
INNER JOIN <Table 3> on train.type_id = train_type.id

train.class\u id上的内部连接=train\u class.id
train.type\u id上的内部连接=train\u type.id

在使用内部联接时，您错过了第2个和第3个表

INNER JOIN <Table 2> on train.class_id = train_class.id
INNER JOIN <Table 3> on train.type_id = train_type.id

train.class\u id上的内部连接=train\u class.id
train.type\u id上的内部连接=train\u type.id

您的代码中有语法错误 join的语法如下所示：

SELECT column_name(s)
FROM table1
JOIN table2
ON table1.column_name=table2.column_name;

因此，您的查询如下所示：

 " SELECT train.id, train.class_id, train.type_id, train.m_year, train_type.type," & _
 " train_type.avarage_speed, train_class.class, train_class.capacity FROM train" & _
 " INNER JOIN train_class on train.class_id = train_class.id " & _
 " INNER JOIN train_type on train.type_id = train_type.id"

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您的数据库中有语法错误 join的语法如下所示：

SELECT column_name(s)
FROM table1
JOIN table2
ON table1.column_name=table2.column_name;

因此，您的查询如下所示：

 " SELECT train.id, train.class_id, train.type_id, train.m_year, train_type.type," & _
 " train_type.avarage_speed, train_class.class, train_class.capacity FROM train" & _
 " INNER JOIN train_class on train.class_id = train_class.id " & _
 " INNER JOIN train_type on train.type_id = train_type.id"

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您正在使用三个表进行联接，但未正确提到联接

连接语法

(table1 INNER JOIN table2 ON table1.ID = table2.ID) INNER JOIN table3 ON table1.ID = table3.ID

您的查询应该是这样的

SELECT train.id,
   train.class_id,
   train.type_id,
   train.m_year,
   train_type.type,
   train_type.avarage_speed,
   train_class.class,
   train_class.capacity
FROM (train
   INNER JOIN train_class
   ON train.class_id = train_class.id)
   INNER JOIN train_type ON train.type_id = train_type.id

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您正在使用三个表进行联接，但未正确提到联接

连接语法

(table1 INNER JOIN table2 ON table1.ID = table2.ID) INNER JOIN table3 ON table1.ID = table3.ID

您的查询应该是这样的

SELECT train.id,
   train.class_id,
   train.type_id,
   train.m_year,
   train_type.type,
   train_type.avarage_speed,
   train_class.class,
   train_class.capacity
FROM (train
   INNER JOIN train_class
   ON train.class_id = train_class.id)
   INNER JOIN train_type ON train.type_id = train_type.id

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您缺少语法、表名，代码必须如下所示：

SELECT train.id,
    train.class_id,
    train.type_id,
    train.m_year,
    train_type.type,
    train_type.avarage_speed,
    train_class.class,
    train_class.capacity
FROM train
    INNER JOIN train_class
ON  train.class_id = train_class.id
    AND train.type_id = train_type.id

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您缺少语法、表名，代码必须如下所示：

SELECT train.id,
    train.class_id,
    train.type_id,
    train.m_year,
    train_type.type,
    train_type.avarage_speed,
    train_class.class,
    train_class.capacity
FROM train
    INNER JOIN train_class
ON  train.class_id = train_class.id
    AND train.type_id = train_type.id