Question

我有以下4个表格。

1. DEBATES. 
   [ID, STARTER_PACK_ID]
2. DEBATE_GROUPS.
   [ID, DEBATE_ID, STAKEHOLDER_ID]
3. DEBATE_STAKEHOLDERS.
   [ID, STARTER_PACK_ID, NAME]
4. DEBATE_STARTER_PACKS.
   [ID]

我正在尝试选择每个辩论组，其中包含每个利益相关者ID，利益相关者ID的名称以及该辩论的计数，以及starter_pack_id等于某个值。例如，必须显示这些，即使计数为0或存在空值

预期结果如下......

DEBATE_ID | STAKEHOLDER_ID | COUNT(Example)
-------------------------------------------
   1             1               2
   1             2               1
   1             3               3
   2             1               4
   2             2               1
   2             3               2

问题是它没有显示未使用的辩论在数据库中，这是我所需要的。我应该在下面的代码中更改什么来检索此信息？

以下是我的尝试......

SELECT 
    a.id, 
    a.name, 
    a.abbreviation, 
    b.debate_id, 
    IF(COUNT(b.stakeholder_id) = 0, 0, COUNT(b.stakeholder_id)) AS total_freq, 
    COUNT(b.stakeholder_id) AS freq 
FROM 
    debate_stakeholders a LEFT JOIN debate_groups b ON b.stakeholder_id = a.id 
GROUP BY
    a.id, b.debate_id 
HAVING 
    COUNT(*) < 3 
ORDER BY 
    a.id,b.debate_id,b.stakeholder_id

Answer 1

SELECT 
    a.id, 
    a.name, 
    a.abbreviation, 
    d.id, 
    IF(COUNT(b.stakeholder_id) = 0, 0, COUNT(b.stakeholder_id)) AS total_freq, 
    COUNT(b.stakeholder_id) AS freq 
FROM 
    debate_stakeholders a LEFT JOIN debate_groups b ON b.stakeholder_id = a.id 
    RIGHT JOIN debates as d ON b.debate_id = d.id
GROUP BY
    a.id, b.debate_id 
HAVING 
    COUNT(*) < 3 
ORDER BY 
    a.id,b.debate_id,b.stakeholder_id

MYSQL左连接表选择数据问题 - 逻辑错误

1 个答案: