Question

我试图计算用户触发以下查询的次数。我已经得出结论，需要一个子查询。以下（不可否认的是，不确定）查询的工作原理是没有子查询。 Sub Query用作独立查询。但经过三天的尝试，我无法将两者结合起来。我不知道我是否有明显的语法错误，或者我是否原则上错了。我需要帮助！

SELECT id, status, FirstName, LastName, Track, KeyChange, Version, 
DATE_FORMAT(CONVERT_TZ(Created,'+00:00','+1:00'), '%l:%i %p') AS Created_formatted, 
TIME_FORMAT(SEC_TO_TIME(TIMESTAMPDIFF(SECOND, pinknoise.Created, CURRENT_TIMESTAMP() - INTERVAL '0' HOUR)),'%Hh %im') AS elapsed,
(SELECT `FirstName`, Count(*) AS 'CountRequests' FROM `pinknoise` GROUP by `FirstName`)
FROM pinknoise 
WHERE status = 'incoming' 
ORDER BY Created DESC

Answer 1

我并不真正了解您的查询应该达到的目标，但格式如下：

SELECT 
    id, 
    status, 
    FirstName, 
    LastName, 
    Track, 
    KeyChange, 
    Version, 
    DATE_FORMAT(
        CONVERT_TZ(
            Created,
            '+00:00',
            '+1:00'
        ), 
        '%l:%i %p'
    ) AS Created_formatted, 
    TIME_FORMAT(
        SEC_TO_TIME(
            TIMESTAMPDIFF(
                SECOND, 
                pinknoise.Created, 
                CURRENT_TIMESTAMP() - INTERVAL '0' HOUR
            )
        ),
        '%Hh %im'
    ) AS elapsed
    (
        SELECT 
            `FirstName`, 
            Count(*) AS 'CountRequests' 
        FROM 
            `pinknoise` 
        GROUP by 
            `FirstName`
    )
FROM 
    pinknoise 
WHERE 
    status = 'incoming' 
ORDER BY 
    Created DESC

我的想象：您希望同一个表中此特定名字的总条目数。肮脏的方式是：

SELECT 
    id, 
    status, 
    FirstName, 
    LastName, 
    Track, 
    KeyChange, 
    Version, 
    DATE_FORMAT(
        CONVERT_TZ(
            Created,
            '+00:00',
            '+1:00'
        ), 
        '%l:%i %p'
    ) AS Created_formatted, 
    TIME_FORMAT(
        SEC_TO_TIME(
            TIMESTAMPDIFF(
                SECOND, 
                pinknoise.Created, 
                CURRENT_TIMESTAMP() - INTERVAL '0' HOUR
            )
        ),
        '%Hh %im'
    ) AS elapsed,
    (
        SELECT 
            Count(*) 
        FROM 
            `pinknoise` AS tb
        WHERE
            tb.FirstName = pinknoise.FirstName
    ) AS CountRequests
FROM 
    pinknoise 
WHERE 
    status = 'incoming' 
ORDER BY 
    Created DESC

更好的表现会有一个加入：

SELECT 
    pinknoise.id, 
    pinknoise.status, 
    pinknoise.FirstName, 
    pinknoise.LastName, 
    pinknoise.Track, 
    pinknoise.KeyChange, 
    pinknoise.Version, 
    DATE_FORMAT(
        CONVERT_TZ(
            pinknoise.Created,
            '+00:00',
            '+1:00'
        ), 
        '%l:%i %p'
    ) AS Created_formatted, 
    TIME_FORMAT(
        SEC_TO_TIME(
            TIMESTAMPDIFF(
                SECOND, 
                pinknoise.Created, 
                CURRENT_TIMESTAMP() - INTERVAL '0' HOUR
            )
        ),
        '%Hh %im'
    ) AS elapsed,
    tabA.CountRequests
FROM 
    pinknoise 
INNER JOIN
    (
        SELECT 
            Count(*) AS 'CountRequests',
            FirstName
        FROM 
            `pinknoise`
        GROUP BY
            FirstName
    ) tabA
ON
    pinknoise.FirstName = tabA.FirstName
WHERE 
    status = 'incoming' 
ORDER BY 
    Created DESC

Answer 2

您的子选择在选择部分中返回2个值，它只需要一个值。我猜你正在获得FirstName以进行连接。如果是这样，那么试试这个：

SELECT 
    p.id, 
    p.status, 
    p.FirstName, 
    p.LastName, 
    p.Track, 
    p.KeyChange, 
    p.Version, 
    DATE_FORMAT(CONVERT_TZ(p.Created,'+00:00','+1:00'), '%l:%i %p') AS Created_formatted, 
    TIME_FORMAT(SEC_TO_TIME(TIMESTAMPDIFF(SECOND, p.Created, CURRENT_TIMESTAMP() - INTERVAL '0' HOUR)),'%Hh %im') AS elapsed,
    cnt.CountRequests
FROM 
    pinknoise p
    inner join (SELECT p.FirstName, Count(*) AS CountRequests FROM pinknoise p GROUP by p.FirstName) cnt on p.FirstName = cnt.FirstName
WHERE 
    p.status = 'incoming' 
ORDER BY 
    p.Created DESC;

MySQL子查询难度

2 个答案: