Question

以下是我的sql：

SELECT DISTINCT
    U.[IP Address],
    U.[Risk Rating],
    COUNT( U.[IP Address] ) AS UNIXIP,
    COUNT( U.[Risk Rating] ) RATINGCOUNT
FROM
    Exception AS E
LEFT JOIN
    tblUNIX_Archive AS U
        ON E.IP_address <> U.[IP Address]  -- Is using '<>' ok? instead of =
        AND (U.ScanDate BETWEEN '2011-01-22' AND '2011-02-18')
group by
    U.[Risk Rating],
    U.[IP Address]
ORDER BY
    U.[Risk Rating],
    U.[IP Address]

我只需要查看tblUNIX_Archive表中不在Exception表中的唯一IP地址。我得到了多个记录。我上面的sql做错了什么？

Answer 1

@Einacio，虽然你的解决方案可行，但我认为在where子句中没有输入会达到性能 - 如果记录更多，可能会非常糟糕。

@Kombucha，您可以尝试以下方法：

    SELECT DISTINCT
    U.[IP Address],
    U.[Risk Rating],
    COUNT( U.[IP Address] ) AS UNIXIP,
    COUNT( U.[Risk Rating] ) RATINGCOUNT
FROM
    tblUNIX_Archive AS U
LEFT JOIN
    Exception AS E
        ON E.IP_address = U.[IP Address]  -- = to is better 
        AND (U.ScanDate BETWEEN '2011-01-22' AND '2011-02-18')
where E.IP_adress is null
group by
    U.[Risk Rating],
    U.[IP Address]
ORDER BY
    U.[Risk Rating],
    U.[IP Address]

更新：注意到连接的表顺序错误...纠正了。

Answer 2

选择一个表中不在另一个表中的记录，你不必使用join，你必须使用NOT IN

SELECT DISTINCT
    U.[IP Address],
    U.[Risk Rating],
    COUNT( U.[IP Address] ) AS UNIXIP,
    COUNT( U.[Risk Rating] ) RATINGCOUNT
FROM
    tblUNIX_Archive AS U
where  U.[IP Address] NOT IN( select E.IP_address  from Exception AS E)
        AND (U.ScanDate BETWEEN '2011-01-22' AND '2011-02-18')
group by
    U.[Risk Rating],
    U.[IP Address]
ORDER BY
    U.[Risk Rating],
    U.[IP Address]

Answer 3

左外连接将返回左表中的行，即使它们在右侧的行中不匹配。由于您需要所有Unix IP地址，因此它们应位于左侧。（或切换到右外连接。）WHERE子句拒绝匹配的行。

SELECT DISTINCT
    U.[IP Address],
    U.[Risk Rating],
    COUNT( U.[IP Address] ) AS UNIXIP,
    COUNT( U.[Risk Rating] ) RATINGCOUNT
FROM
    tblUNIX_Archive AS U left outer join
    Exception AS E ON E.IP_address = U.[IP Address] AND
        (U.ScanDate BETWEEN '2011-01-22' AND '2011-02-18')
WHERE
    E.IP_address is NULL
group by
    U.[Risk Rating],
    U.[IP Address]
ORDER BY
    U.[Risk Rating],
    U.[IP Address]

帮助左连接

3 个答案: