Question

以下查询将返回所有“阻止”用户和所有“已阻止”用户。相当直接的查询。

$stmt=$db->prepare('SELECT blocker,blocked FROM list_blocked 
                    WHERE (blocked = :username AND blocker <> :username) 
                    OR (blocker = :username AND blocked <> :username)');
$stmt->bindParam(':username', $username);
$stmt->execute();

下一个查询将返回除当前$ username之外的members表中的所有用户名。

$query = $db->prepare("SELECT username FROM members WHERE username <> :username");
$query->bindValue(':user', $username;
$query->execute();
$row = $query->fetchAll();

我需要的是从第一个查询的结果中获取所有值的方法，不包括活动的$ username，然后从第二个查询中排除所有这些结果。

例如：

Example results of first query:
jim blocked joe
larry blocked joe
steve blocked joe
joe blocked tony
jack blocked joe

Those results applied to the second query would look something like:
$query = $db->prepare("SELECT username FROM members WHERE username <> :username 
                       AND username <> jim 
                       AND username <> larry
                       AND username <> steve
                       AND username <> tony
                       AND username <> jack");

我将如何实现这样的目标？

更新：

所以我试图使用子查询，但它一直返回“操作数应该包含1列”

SELECT username FROM members WHERE username NOT IN (
    SELECT blocker,blocked FROM list_blocked 
                           WHERE (blocked = 'viraladmin' AND blocker <> 'viraladmin') 
                           OR (blocker = 'viraladmin' AND blocked <> 'viraladmin')
 )

另一个更新：

我试图使用内部联接来实现这一点，但是结果总是返回空，我认为这是因为实际上没有任何东西可以加入。

SELECT members.username, list_blocked.blocker, list_blocked.blocked
FROM members
INNER JOIN list_blocked 
ON members.username = list_blocked.blocker
AND members.username = list_blocked.blocked
WHERE members.username <>  'username' 
AND (list_blocked.blocked = 'username' AND list_blocked.blocker <> 'username') 
OR (list_blocked.blocker = 'username' AND list_blocked.blocked <> 'username')

Answer 1

您可以使用子查询完成此操作：

SELECT username FROM members WHERE username NOT IN (
SELECT blocker,blocked FROM list_blocked 
                WHERE (blocked = :username AND blocker <> :username) 
                OR (blocker = :username AND blocked <> :username)
 )

已编辑 - 为了适合您需要在子查询中进行联合的SQL查询，因此结果不会返回一列。：

SELECT username FROM members WHERE username NOT IN (
   SELECT blocker as username FROM list_blocked 
                WHERE (blocked = :username AND blocker <> :username) 
                OR (blocker = :username AND blocked <> :username)
   UNION
   SELECT blocked as username FROM list_blocked 
                WHERE (blocked = :username AND blocker <> :username) 
                OR (blocker = :username AND blocked <> :username)
 )

Answer 2

您也可以使用LEFT JOIN - NULL模式。

SELECT username
FROM members AS m
LEFT JOIN list_blocked AS b
ON m.username IN (b.blocker, b.blocked)
    AND ((blocked = :username AND blocker <> :username) 
        OR (blocker = :username AND blocked <> :username))
WHERE b.blocked IS NULL

这是基于Return row only if value doesn't exist

中的模式

php PDO MySQL根据另一个表的结果数组选择一个表的结果

2 个答案: