MySQL選擇與左連接不同？

Question

我想獲得一個沒有公司級筆記的company_id列表。 但是，該公司可能有位置級別的說明。

company
-------------------------
company_id  name  deleted
1           Foo   0
2           Bar   0
3           Baz   0

location
-----------------------
location_id  company_id
6            1
7            2
8            3

note
-----------------------------------------
note_id  company_id  location_id  deleted
10       2           6            0         // location-level note
11       1           7            0         // location-level note
12       null        8            0         // location-level note
13       2           null         0         // company-level note

我希望我的結果表是這樣的：

company_id  name
1           Foo
3           Baz

更新

Foo / company_id = 1沒有公司級別的注釋，因為該注釋還具有location_id ，這使其成為位置級別注釋。 公司級別的票據是僅鏈接到公司（而非位置）的票據。

更新結束

我已經嘗試過做這樣的事情，但是它返回一個空集，所以我不確定它是否有效，並且沒有任何公司沒有公司級別的注釋或者我做錯了什么。

SELECT DISTINCT 
c.company_id, 
c.name
FROM company AS c
LEFT JOIN note AS n
ON c.company_id = n.company_id
WHERE 
c.deleted = 0 AND
n.deleted = 0 AND
n.location_id IS NOT NULL AND 
n.location_id != 0 AND
c.company_id = (SELECT MAX(company_id) FROM company)

Mike修改的接受的答案

SELECT
    company_id,
    name
FROM company
WHERE 
    deleted = 0 AND
    company_id NOT IN (
        SELECT DISTINCT 
            c.company_id
        FROM company AS c 
        INNER JOIN note AS n 
        ON c.company_id = n.company_id 
        WHERE (
            n.deleted = 0 AND
                (n.location_id IS NULL OR 
                n.location_id = 0)
        )
    );

Answer 1

考慮這一點的最簡單方法是首先找到所有具有公司級別備注的公司，您可以這樣做

 select distinct c.company_id
   from company c 
 inner join notes n 
     on c.company_id = n.company_id 
  where n.location_id is null;

然后只需從公司中刪除這些公司選擇：

select company_id,
       name
  from company
 where company_id not in (select distinct c.company_id
                            from company c 
                          inner join notes n 
                              on c.company_id = n.company_id 
                           where n.location_id is null);

*已更新以使用內部聯接而不是逗號分隔的聯接。

Answer 2

SELECT DISTINCT c.* 
  FROM company c 
  LEFT 
  JOIN note n 
    ON n.company_id = c.company_id 
   AND n.location_id IS NULL 
 WHERE n.note_id IS NULL;