如何从左侧外部联接中查找具有AND条件的完全匹配项

Question

我有一个MySQL表
Booktable

+--------+-------------+-----+  
| bookno | bookname    | ... |  
+--------+-------------+-----+  
| 1      | FINALFANTASY| ... |  
+--------+-------------+-----+  

Authortable

+--------+-------------+-----+  
| bookno | Authorname  | ... |  
+--------+-------------+-----+  
| 1      | SQUARE      | ... |  
+--------+-------------+-----+  
| 1      | ENIX        | ... |  
+--------+-------------+-----+  

因此，我想进行搜索以获取与结果相符的书。

我尝试

select b.bookname,a.authorname from booktable as b 
left outer join authortable a on b.bookno = a.bookno
where a.authorname = "square" and a.authorname = "enix"

它仅适用于一个where condition。但是当我尝试使用两个authorname时，没有找到结果。 我该怎么办 ？

（此查询使用“ OR”但不使用“ AND”，但我确实希望该值与搜索条件匹配，或者如果某些搜索条件不匹配但不为空，则不应显示该值（因此它不能在这个案例）

Answer 1

使用汇总来确定哪些书籍同时具有您想要的作者：

SELECT t1.bookname,
       t2.authorname
FROM booktable t1
INNER JOIN authortable t2
    ON t1.bookno = t2.bookno
INNER JOIN
(
    SELECT bookno
    FROM authortable
    WHERE authorname IN ('square', 'enix')
    GROUP BY bookno
    HAVING COUNT(DISTINCT authorname) = 2
) t3
    ON t1.bookno = t3.bookno

演示在这里：

SQLFiddle

Answer 2

Tim Biegeleisen的答案很好，但是如果您需要完全匹配，则下面的最后一个SQL是正确的：

SELECT * FROM book;
SELECT * FROM author;

/* this SQL will return book's author name more than 2 also true */
SELECT b.bookname, a.authorname
FROM book AS b
JOIN author AS a ON b.bookno = a.bookno
JOIN (
  SELECT bookno FROM author
  WHERE authorname in ('SQUARE', 'ENIX')
  GROUP BY 1
  HAVING count(*) = 2
) AS a2 ON b.bookno = a2.bookno;

/* this sQL will return only 2 and all matched authors: */
SELECT b.bookname, a.authorname
FROM book AS b
JOIN author AS a ON b.bookno = a.bookno
JOIN (
  SELECT bookno FROM author
  WHERE authorname in ('SQUARE', 'ENIX')
  GROUP BY 1
  HAVING count(*) = 2
) AS a2 ON b.bookno = a2.bookno
JOIN (
  SELECT bookno FROM author 
  GROUP BY 1 
  HAVING count(distinct authorname) = 2
) AS a3 ON b.bookno = a3.bookno

PS1-无需左加入

PS2-无需计数-除非您的作者表设计不正确

如果标题为FANTASY，则流派为Adventure，fantasy，搜索条件为

[冒险] =找到

[幻想] =找到

[冒险，幻想] =找到

[冒险，幻想，动作] =找不到

然后，SQL将是：

SELECT b.bookname, a.authorname
FROM book AS b
JOIN author AS a ON b.bookno = a.bookno
JOIN author AS a1 ON b.bookno = a1.bookno AND a1.authorname = 'SQUARE'
JOIN author AS a2 ON b.bookno = a2.bookno AND a2.authorname = 'ENIX'

以上工作正常，我想知道是否可以提高性能