SQL 只显示一个订单行的订单。如果更多行不显示任何内容

Question

我正在尝试搜索订单行中包含一篇特定文章的订单，但如果有不止一行，我不想看到任何行。

这是两个订单的示例，我只想获得一个结果。订单9891026有两行，9891025只有一行。

    select  order_no, line_no
    from customer_order_line
    where order_no in('9891026','9891025')

结果

order_no	line_no
9891026	1
9891026	2
9891025	1

我只想得到

order_no	line_no
9891025	1

我不知道如何对此进行正确的查询。

Answer 1

一种方法是检查订单 exists 的 line_no 是否大于 1:

select ol.order_no, ol.line_no
from customer_order_line ol
where ol.order_no in (9891026, 9891025)
and not exists (
  select * from customer_order_line x
  where x.order_no = ol.order_no and x.line_no > 1
);

Answer 2

或者，您可以执行 GROUP BY 并使用 HAVING 确保只有一行。

select ol.order_no, min(ol.line_no)
from customer_order_line ol
where ol.order_no in ('9891026', '9891025')
group by ol.order_no
having count(*) = 1

Answer 3

首先查找单行订单号 order_no（子查询），然后仅从具有这些订单号的订单中查找 select。请注意，连接查询（虽然可能更难阅读）可能更有效。

select * 
from customer_order_line 
where order_no in
(
 select order_no 
 from customer_order_line
 group by order_no 
 having count(*) = 1
) -- this is the list of single-item orders
and order_no in (9891026,9891025) -- this is the list of target orders

SQL 只显示一个订单行的订单。如果更多行不显示任何内容

SQL only show orders with one order row. if more rows don display anything

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