即使不在联合表内也返回结果

Question

谁能帮我完成这个任务？假设我有 2 张桌子：

_表 1“出版商”：ASIN、价格、出版商_ID

_表 2“违规”：ASIN、Publisher_ID、Previous_Violations (Y/N)、ID

现在我有了这个

    SET @PUB = "

    'A','B','C','D',

    " 
    SELECT p.publisher_ID, count(distinct v.id) as "Number of Violations"
    FROM Publisher p
    LEFT JOIN Violations v
    ON p.publisher_ID = v.publisher_ID
    and p.Previous_Violations = 'Y'
    
    WHERE 
    p.publisher_ID IN (",@PUB,")
    GROUP BY p.publisher_ID

我想查看@PUB 列表中所有发布者的历史违规行为。所以会有4种情况：

1. @PUB 中的所有发布者都存在两个表
2. @PUB 中有发布者存在于表 1 中，但不存在于表 2 中。
3. @PUB 中存在表 2 中存在的发布者，但表 1 中不存在。
4. @PUB 中的发布者在 2 个表中都不存在。

为了澄清，假设酒吧 A 和 B 存在于两个表中，C 存在于表 1（不是 2）中，D 存在于表 2（但不是 1）中，并且 E 都不存在于任何一个中。

现在我上面的查询只给出（由于左连接）

一个 3

B 2

C 4

但我希望它显示：

一个 3

B 2

C 4

D 6

E 空

Answer 1

如果您没有大列表，您可以尝试以下操作，您也许可以创建一个为您生成查询的过程

(
    SELECT p.publisher_ID, sum(IF(v.Previous_Violations = 'Y', 1, 0)) AS "Number of Violations"
    FROM (SELECT 'A' AS publisher_ID) AS p LEFT JOIN Violations v USING(publisher_ID) 
    GROUP BY p.publisher_ID
)
UNION
(
     SELECT p.publisher_ID, sum(IF(v.Previous_Violations = 'Y', 1, 0)) AS "Number of Violations"
    FROM (SELECT 'B' AS publisher_ID) AS p LEFT JOIN Violations v USING(publisher_ID) 
    GROUP BY p.publisher_ID)
UNION
(
     SELECT p.publisher_ID, sum(IF(v.Previous_Violations = 'Y', 1, 0)) AS "Number of Violations"
    FROM (SELECT 'C' AS publisher_ID) AS p LEFT JOIN Violations v USING(publisher_ID) 
    GROUP BY p.publisher_ID)
UNION
(
     SELECT p.publisher_ID, sum(IF(v.Previous_Violations = 'Y', 1, 0)) AS "Number of Violations"
    FROM (SELECT 'D' AS publisher_ID) AS p LEFT JOIN Violations v USING(publisher_ID) 
    GROUP BY p.publisher_ID
)
UNION
(
     SELECT p.publisher_ID, sum(IF(v.Previous_Violations = 'Y', 1, 0)) AS "Number of Violations"
    FROM (SELECT 'E' AS publisher_ID) AS p LEFT JOIN Violations v USING(publisher_ID) 
    GROUP BY p.publisher_ID
)