Question

我有以下MySQL表来记录学生的注册状态变化：

CREATE TABLE `pupil_registration_statuses` (
`status_id` INT(11) NOT NULL AUTO_INCREMENT,
`status_pupil_id` INT(10) UNSIGNED NOT NULL,
`status_status_id` INT(10) UNSIGNED NOT NULL,
`status_effectivedate` DATE NOT NULL,
PRIMARY KEY (`status_id`),
INDEX `status_pupil_id` (`status_pupil_id`)
)
COLLATE='utf8_general_ci'
ENGINE=MyISAM;

示例数据：

INSERT INTO `pupil_registration_statuses` (`status_id`, `status_pupil_id`, `status_status_id`, `status_effectivedate`) VALUES
    (1, 123, 1, '2013-05-06'),
    (2, 123, 2, '2014-03-15'),
    (3, 123, 5, '2013-03-15'),
    (4, 123, 6, '2013-05-06'),
    (5, 234, 2, '2013-02-02'),
    (6, 234, 4, '2013-04-17'),
    (7, 345, 2, '2014-02-01'),
    (8, 345, 3, '2013-06-01');

可能会插入状态，因此日期序列不一定遵循相同的ID序列。

例如：status_id 1的日期可能是2013-05-06，但status_id 3的日期可能是2013-03-15。

但是，

status_id值在任何特定日期内都是连续的。因此，如果学生的注册状态在一天内多次更改，那么最后一行将反映他们在该日期的状态。

有必要在特定日期找出特定学生的注册状态。以下查询适用于个别学生：

SELECT * 
FROM pupil_registration_statuses 
WHERE status_pupil_id = 123
    AND status_effectivedate <= '2013-05-06'
ORDER BY status_effectivedate DESC, status_id DESC
LIMIT 1;

这将返回预期的status_id = 4

行

但是，我现在需要发出一个（单个）查询来返回特定日期所有学生的状态。

建议使用以下查询，但不会在一天内遵守＆＃34;最后status_id＆＃34;要求：

SELECT *
FROM pupil_registration_statuses prs
    INNER JOIN (SELECT status_pupil_id, MAX(status_effectivedate) last_date
        FROM pupil_registration_statuses
        WHERE status_effectivedate <= '2013-05-06'
        GROUP BY status_pupil_id) qprs ON prs.status_pupil_id = qprs.status_pupil_id AND prs.status_effectivedate = qprs.last_date;

但是，此查询为pupil 123返回2行。

修改

为了澄清，如果输入是日期'2013-05-06'，我希望从查询中获得第4行和第6行。

http://sqlfiddle.com/#!2/68ee6/2

Answer 1

这就是你要追求的吗？

SELECT a.*
  FROM pupil_registration_statuses a
  JOIN
     ( SELECT prs.status_pupil_id
            , MIN(prs.status_id) min_status_id
         FROM pupil_registration_statuses prs
         JOIN 
            ( SELECT status_pupil_id
                   , MAX(status_effectivedate) last_date
                FROM pupil_registration_statuses
               WHERE status_effectivedate <= '2013-05-06'
               GROUP
                  BY status_pupil_id
            ) qprs 
           ON prs.status_pupil_id = qprs.status_pupil_id 
          AND prs.status_effectivedate = qprs.last_date
        GROUP
           BY prs.status_pupil_id
     ) b
    ON b.min_status_id = a.status_id;

http://sqlfiddle.com/#!2/68ee6/7

（顺便说一句，对于这类问题，这是一个丑陋且无证件的黑客攻击：

SELECT x.* FROM (SELECT * FROM prs WHERE status_effectivedate <= '2013-05-06' ORDER BY status_pupil_id, status_effectivedate DESC, status_id)x GROUP BY status_pupil_id;

......但我没有告诉你那个！ ;））

Answer 2

我已经更改了where子句，请尝试一下。

SELECT *
    FROM pupil_registration_statuses prs
        INNER JOIN (SELECT status_pupil_id, MAX(status_effectivedate) last_date
            FROM pupil_registration_statuses
            WHERE Datediff(status_effectivedate, '2013-05-06') <= 0
            GROUP BY status_pupil_id) qprs ON prs.status_pupil_id = qprs.status_pupil_id AND prs.status_effectivedate = qprs.last_date;

修改

试试这个

SELECT *
    FROM 

        (
            select status_pupil_id,max(status_id) as status_id from pupil_registration_statuses innr
            --where Datediff(dd,status_effectivedate, '2013-05-06') >= 0
            group by status_pupil_id

        )as ca 
        inner join pupil_registration_statuses prs on prs.status_id = ca.status_id
where   Datediff(dd,prs.status_effectivedate, '2013-05-06') >= 0

Answer 3

如果我理解正确，你想......

1）每人一排。

2）从您手动输入的特定日期获取状态更改。

3）从特定日期内获取最后一次状态更改。

如果这是正确的，您需要按日期排序的查询，然后按ID排序，只需distinct。

SELECT DISTINCT on status_pupil_id *
FROM pupil_registration_statuses 
WHERE status_pupil_id = 123
    AND status_effectivedate <= '2013-05-06'
ORDER BY status_effectivedate DESC, status_id DESC

用于查找＆＃34; LAST＆＃34;的MySQL查询行，基于两个字段

3 个答案: