SQL-在某些条件下选择查询的问题

Question

我有这两个表，在第一个表（WRITES）中，有几本书存储在数据库中（DOI代表该书的代码，而ORCID是该书的作者，在第二个表（QUOTES）中，每个表中都有引号书）。我要达到的结果是，使作者的识别码在他们的书中提到其他作者而非自己写的书]

WRITES

Doi   Orcid
1     100
2     200
3     300
4     100

QUOTES

Doi DoiMentioned
1          4
2          3
3          4

预期输出：]

ORCID Doi    DoiMentioed
200    2         3
300    3         4

我的代码：

(select w.orcid
from writes w
join quotes q
on q.doi = w.doi

minus

select w.orcid
from writes w
join quotes q
on q.doimentioned = w.doi);

我也尝试了内部联接，但结果不是我希望的

Answer 1

内部联接应该起作用，但是您需要使用WRITES表两次：一次用于提到作者，一次用于提到作者。然后比较它们以确保它们不同。

SELECT w.orcid, w.doi, q.doimentioned
FROM    writes w
INNER JOIN quotes q on q.doi = w.doi
INNER JOIN writes w2 ON w2.doi = q.doiMentioned
WHERE w2.orcid != w.orcid;

完整示例，带有来自OP的数据，以显示其工作原理：

WITH writes (doi, orcid) AS 
  ( SELECT 1, 100 FROM DUAL UNION ALL
    SELECT 2, 200 FROM DUAL UNION ALL
    SELECT 3, 300 FROM DUAL UNION ALL
    SELECT 4, 100 FROM DUAL ),
  quotes ( Doi, DoiMentioned ) AS 
  ( SELECT 1,4 FROM DUAL UNION ALL
    SELECT 2,3 FROM DUAL UNION ALL
    SELECT 3,4 FROM DUAL )
SELECT w.orcid, w.doi, q.doimentioned
FROM    writes w
INNER JOIN quotes q on q.doi = w.doi
INNER JOIN writes w2 ON w2.doi = q.doiMentioned
WHERE w2.orcid != w.orcid;

+-------+-----+--------------+
| ORCID | DOI | DOIMENTIONED |
+-------+-----+--------------+
|   200 |   2 |            3 |
|   300 |   3 |            4 |
+-------+-----+--------------+