mysql - 如果右字段存在，左连接如何使用

Question

我有两个表:

用户(查询中使用的字段)->

 |uuid|name|last_name|email|rol        |status|
 |1234|abcd|   abc   |1@2.3|pre-thunder|  1   |
 |5678|efgh|   efg   |4@5.6|pre-thunder|  1   | 

以及documentation_thunder表(查询中使用的字段)->

|id|id_thunder|doc_type|
|1 |1234      |image   |

我尝试获取左表中的所有记录，但另外我还从右表中获取计数:

SELECT 
 users.uuid,
 users.email,
 users.name,
 users.last_name, 
 COUNT(documentation_thunder.id) as documentation// i need to know how many documents have the user
FROM users 
LEFT JOIN documentation_thunder
  ON users.uuid = documentation_thunder.id_thunder 
WHERE 
 users.status = 1 AND users.rol = 'pre-thunder' AND (documentation_thunder.doc_type = 'image' OR documentation_thunder.doc_type IS NULL)

此查询仅返回第一个用户，但我需要返回所有用户，无论是否有文档。

有什么想法吗？我该怎么做？

Answer 1

由于您想要为每个用户返回计数，因此您还应该使用group by。也许这就是您所追求的:

SELECT 
 users.uuid,
 users.email,
 users.name,
 users.last_name, 
 COUNT(documentation_thunder.id) as documentation
FROM users 
LEFT JOIN documentation_thunder
  ON users.uuid = documentation_thunder.id_thunder 
WHERE 
 users.status = 1 AND users.rol = 'pre-thunder' AND 
 (documentation_thunder.doc_type = 'image' OR documentation_thunder.doc_type IS NULL)
GROUP BY users.uuid