Question

我很难加入Oracle中的三个单独的表格。我之前从未参加过三张桌子，所以我并不精通。我的理论如下：

SELECT customer_num WHEN customer_num IS 104 -198, order_num
  FROM orders INNER JOIN items
    ON order_num, stock_num
    INNER JOIN stock
      ON stock_num, description

基本上，我正在尝试从ORDERS表开始，并从订单表中提取客户编号（customer_num），特别是客户编号104 -108和order_num 。然后将订单表附加到Items表并附加order_num和stock_num，最后附上stock表并提取stock_num和说明。

Answer 1

您的语法遍布整个地方，不适用于双表连接，甚至不能查询单个表。不知道你从哪里获得WHEN，或者你的条款的顺序。请查看SQL reference，了解如何加入以及如何过滤。总之...

你似乎想要这样的东西：

SELECT o.customer_num, o.order_num, i.stock_num, s.description
FROM orders o
INNER JOIN items i ON i.order_num = o.order_num
INNER JOIN stock s ON s.stock_num = i.stock_num
WHERE o.customer_num BETWEEN 104 AND 198;

WHERE子句正在应用于orders表，以限制您获得的客户订单。我假设您的说明中orders和items表格中有一个共同的order_num列，您可以参与其中;并且items和stock表格中包含您可以加入的常见stock_num列。

正如OldProgrammer所说，将表格模式包含在问题中是有帮助的，因此不需要做出假设，并且显示样本数据和该数据的预期输出将阐明您正在尝试做什么。 / p>

Answer 2

看起来应该是这样的（基于有关架构的有限信息）......

SELECT 
    O.CUSTOMER_NUM, 
    O.ORDER_NUM, 
    S.STOCK_NUM,
    S.DESCRIPTION
FROM 
    ORDERS O,
    ITEMS I,
    STOCK S
WHERE
    I.CUSTOMER_NUM >= 104
    AND I.CUSTOMER_NUM <= 198
    AND O.ORDER_NUM = I.ORDER_NUM
    AND I.STOCK_NUM = S.STOCK_NUM

Answer 3

JOIN的语法是：

TableExpression [ INNER ] JOIN TableExpression
{
  ON booleanExpression |    USING clause
}

booleanExpression是表将链接的内容。所以，在你的例子中，像这样：

SELECT customer_num WHEN customer_num IS 104 -198, order_num
FROM orders INNER JOIN items
  ON orders.<some_column> = items.<some_column>
INNER JOIN stock
  ON items.<some_column> = stock.<some_column>

你如何加入Oracle中的三个表？

3 个答案: