Question

我需要找到至少有1个发行记录的所有顾客。这是我现在拥有的，但它只找到一个结果。我做错了什么？

SELECT * 
FROM patrons 
    INNER JOIN circulations on circulations.patron_id = patrons.id 
HAVING COUNT(circulations.id) > 0

我没有给表结构，因为我认为解决方案不需要它。如果需要，请告诉我，我会尝试将其添加到问题

Answer 1

怎么样：

SELECT * FROM patrons 
WHERE EXISTS (SELECT 1 FROM circulations 
              WHERE circulations.patron_id = patrons.id)

Answer 2

以下内容应该有效：

SELECT * 
FROM patrons 
    INNER JOIN circulations on circulations.patron_id = patrons.id 
GROUP BY patrons.id

Answer 3

查看我的样本：

假设PatronName是顾客桌上的一栏。

SELECT PatronName,COUNT(circulations.id) as CountCirculation
FROM patrons 
    INNER JOIN circulations on circulations.patron_id = patrons.id 
group by PatronName
HAVING COUNT(circulations.id) > 0

此致

Answer 4

尝试......

select *
from patrons p
left join circulation c on c.patron_id = p.id
where not c.patron_id is null

表连接与count（）条件

4 个答案: