我的SQL SELECT语句有问题。我得到了正确的顺序，正确的驱动程序，但我的其他列不正确！我无法正确地做到这一点。
我有这样的数据：
id, races_id, drivers_id, drive_nr, lap_nr, time, dnf
"231", "9", "41", "1", "1", "00:00:04.750", "0"
"232", "9", "41", "1", "2", "00:00:06.030", "0"
"233", "9", "41", "1", "3", "00:00:01.740", "0"
"234", "9", "42", "1", "1", "00:00:05.440", "0"
"235", "9", "42", "1", "2", "00:00:05.400", "0"
"236", "9", "42", "1", "3", "00:00:02.300", "0"
"237", "9", "43", "1", "1", "00:00:00.620", "0"
"238", "9", "43", "1", "2", "00:00:00.290", "0"
"239", "9", "43", "1", "3", "00:00:00.280", "0"
"240", "9", "44", "1", "1", "00:00:00.600", "0"
"241", "9", "44", "1", "2", "00:00:00.190", "0"
"242", "9", "44", "1", "3", "00:00:00.220", "0"
"243", "9", "45", "1", "1", "00:00:02.830", "0"
"244", "9", "45", "1", "2", "00:00:01.890", "0"
"245", "9", "45", "1", "3", "00:00:03.200", "0"
"246", "9", "46", "1", "1", "00:00:03.580", "0"
"247", "9", "46", "1", "2", "00:00:04.550", "0"
"248", "9", "46", "1", "3", "00:00:01.060", "0"
"249", "9", "47", "1", "1", "00:00:02.920", "0"
"250", "9", "47", "1", "2", "00:00:03.950", "0"
"251", "9", "47", "1", "3", "00:00:00.320", "0"
"252", "9", "48", "1", "1", "00:00:02.150", "0"
"253", "9", "48", "1", "2", "00:00:05.720", "0"
"254", "9", "48", "1", "3", "00:00:04.530", "0"
"255", "9", "49", "1", "1", "00:00:01.530", "0"
"256", "9", "49", "1", "2", "00:00:04.360", "0"
"257", "9", "49", "1", "3", "00:00:07.110", "0"
"258", "9", "50", "1", "1", "00:00:00.450", "0"
"259", "9", "50", "1", "2", "00:00:03.550", "0"
"260", "9", "50", "1", "3", "00:00:07.900", "0"
查询：
SELECT `id` ,
`races_id` ,
`drivers_id` ,
`drive_nr` ,
`lap_nr` ,
MIN( `time` ) AS TIME,
`dnf`
FROM `laps`
WHERE `races_id` =9
GROUP BY drivers_id`
ORDER BY MIN( `time` ) ASC
我明白了：
id, races_id, drivers_id, drive_nr, lap_nr, time, dnf
240, 9, 44, 1, 1, 00:00:00.190, 0
237, 9, 43, 1, 1, 00:00:00.280, 0
249, 9, 47, 1, 1, 00:00:00.320, 0
258, 9, 50, 1, 1, 00:00:00.450, 0
246, 9, 46, 1, 1, 00:00:01.060, 0
255, 9, 49, 1, 1, 00:00:01.530, 0
231, 9, 41, 1, 1, 00:00:01.740, 0
243, 9, 45, 1, 1, 00:00:01.890, 0
252, 9, 48, 1, 1, 00:00:02.150, 0
234, 9, 42, 1, 1, 00:00:02.300, 0
所以我按照正确的顺序获得了正确的时间列，但没有像ID, drive_nr, lap_nr, dnf
如何修复我的查询以获得具有正确其他数据的最短时间的不同drivers_id？
答案 0 :(得分：0)
如果您删除“GROUP BY”
SELECT `id` , `races_id` , `drivers_id` , `drive_nr` , `lap_nr` , MIN( `time` ) AS TIME, `dnf` FROM `laps` WHERE `races_id` = 9 ORDER BY MIN( `time` ) ASC
答案 1 :(得分：0)
问题在于GROUP BY将行组合在一起以形成聚合函数。在标准SQL中，返回的每个列必须是group by子句或聚合字段中提到的，但是MySQL扩展了它。
但是，虽然MySQL确实允许返回额外的列，但它没有指定这些列的值来自哪一行。虽然有一种模式（似乎是我认为插入的最后一行），但这没有定义，可能会改变。
要获得其他字段，您有几个选择。
最简单的是有一个子查询获取驱动程序ID和该驱动程序ID的一圈的最小时间，然后将其连接到laps表（加入驱动程序ID和时间）top获取值匹配行的其他字段。这有几个小的缺点。首先，MySQL不会在子查询的字段上使用索引来连接到主表，但是数据有限可能不是问题（超出了在慢查询日志中弹出的查询的烦恼）。第二个问题是如果有人在两圈之间分享最佳单圈时间。
sql的简单示例： -
SELECT a.id,
a.races_id,
a.drivers_id,
a.drive_nr,
a.lap_nr,
mt.min_time,
a.dnf
FROM laps a
INNER JOIN
(
SELECT drivers_id ,
MIN( `time` ) AS min_time
FROM laps
WHERE races_id = 9
GROUP BY drivers_id
) mt
ON a.drivers_id = mt.drivers_id
AND a.`time` = mt.min_time
WHERE a.races_id = 9
ORDER BY min_time ASC
如果你有相同的最小单圈时间的2圈，那么你需要指定返回哪些细节（或者你可能不关心，并且可能只是在外部查询上滥用GROUP BY）。
第二种解决方案是，您可以根据驱动程序ID和单圈时间为结果生成每行的序列号，并在更改驱动程序ID时重置序列号。然后丢弃没有1序列的任何一圈。但是当你有大量数据时，读取更难，并且可能非常慢。
示例如下（未测试）： -
SELECT id,
races_id,
drivers_id,
drive_nr,
lap_nr,
`time`,
dnf
FROM
(
SELECT id,
races_id,
drivers_id,
drive_nr,
lap_nr,
`time`,
dnf,
@ctr := IF(drivers_id = @did, @ctr + 1, 1) AS ctr,
@did := drivers_id
FROM
(
SELECT id,
races_id,
drivers_id,
drive_nr,
lap_nr,
`time`,
dnf
FROM laps
WHERE races_id = 9
ORDER BY drivers_id, `time`
)
CROSS JOIN
(
SELECT @ctr := 0, @did := 0
) sub1
) sub2
WHERE ctr = 1
ORDER BY `time`