Question

语法问题是什么？我试图做INNER JOIN 3个表，但我收到以下错误消息

其他信息：关键字＆＃39; on＆＃39;附近的语法不正确。

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 
            ON  train.class_id = train_class.id
            AND train.type_id = train_type.id

Answer 1

使用INNER JOIN时，您错过了第2和第3张桌子。

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

Answer 2

join.中存在语法错误 join的语法如下：

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

因此，您的查询将如下所示：

 " 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"

Answer 3

您使用三个表进行JOIN但未提及正确加入

加入语法

(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

Answer 4

你有错过的语法，表名，你的代码必须是：

#header h1 { margin-top; 0}

vb.net INNER加入3个表：附加信息：关键字＆＃39; on＆＃39;

4 个答案: