Question

我正在尝试使用我的查询来查找与animal.wild没有任何关系的特定Worker.wname为真。

例如从下表中我需要返回＆＃34; Yossi＆＃34;因为他没有使用wild = t

的行

wname |   type    | wild 
-------+-----------+------
 David | Capricorn | f
 David | goat      | f
 David | Lamb      | f
 David | Tiger     | t
 David | wolf      | t
 David | Wolf      | t
 Yossi | Capricorn | f
 Yossi | goat      | f

这是我到目前为止的查询（返回上面的表）：

SELECT
    worker.wname, animal.type, animal.wild
FROM resposibility
LEFT JOIN worker ON resposibility.wid = worker.wid
LEFT JOIN cage ON resposibility.cno = cage.cno
LEFT JOIN animal ON cage.cno = animal.cno
GROUP BY worker.wname, animal.wild, animal.type
ORDER BY worker.wname

Answer 1

SELECT worker.wname
FROM resposibility
LEFT JOIN worker ON resposibility.wid = worker.wid
LEFT JOIN cage ON resposibility.cno = cage.cno
LEFT JOIN animal ON cage.cno = animal.cno
GROUP BY worker.wname
HAVING sum(case when animal.wild = 't' then 1 else 0 end) = 0
ORDER BY worker.wname

Answer 2

您只需要表worker，最简单的方法是使用NOT IN运算符：

SELECT DISTINCT wname
FROM resposibility
WHERE wname NOT IN (SELECT wname FROM resposibility WHERE wild='t')
ORDER BY wname

Answer 3

您还可以使用bool_or，如下所示：

SELECT worker.wname
    FROM resposibility
        LEFT JOIN worker ON resposibility.wid = worker.wid
        LEFT JOIN cage ON resposibility.cno = cage.cno
        LEFT JOIN animal ON cage.cno = animal.cno
GROUP BY worker.wname
having bool_or(animal.type) is false
ORDER BY worker.wname

在LEFT JOIN中逐个忽略多个记录

3 个答案: