我有下表：
这是完整表格：http://sqlfiddle.com/#!9/59e05b/5
我需要按event_time和特定访问者对记录进行排序，然后找到字段之间的时差。
我写了以下查询：
SELECT
A.id, A.visitor_id, A.field_label, A.field_number, A.form_step_num, A.field_type, A.event_time, B.event_time, B.event_time - A.event_time as timediff
FROM form_events A
INNER JOIN form_events B
ON B.id = (A.id + 1)
and A.visitor_id = B.visitor_id
and A.form_unique_identifier = B.form_unique_identifier ORDER BY A.event_time ASC
但是问题是它给出了错误的结果。如何在不使用B.id =（A.id + 1）的情况下获取下一个事件时间？
这是我需要的正确输出：
id visitor_id field_label field_number form_step_num field_type event_time event_time timediff
1 455 Your Name (required) 5 1 input 2018-08-28T08:14:00Z 2018-08-28T08:14:03Z 3
2 455 Your Email (required) 6 1 input 2018-08-28T08:14:03Z 2018-08-28T08:14:03Z 0
4 455 Your Name (required) 5 1 input 2018-08-28T08:14:03Z 2018-08-28T08:14:06Z 3
3 455 Your Email (required) 6 1 input 2018-08-28T08:14:06Z 2018-08-28T08:14:10Z 4
5 455 Subject 7 1 input 2018-08-28T08:14:10Z 2018-08-28T08:14:10Z 0
6 455 Your Email (required) 6 1 input 2018-08-28T08:14:10Z 2018-08-28T08:14:13Z 3
7 455 Subject 7 1 input 2018-08-28T08:14:13Z 2018-08-28T08:14:13Z 0
9 455 Your Message 8 1 textarea 2018-08-28T08:14:13Z 2018-08-28T08:14:13Z 0
10 455 Your Message 8 1 textarea 2018-08-28T08:14:13Z 2018-08-28T08:14:15Z 2
8 455 form 0 1 form 2018-08-28T08:14:15Z 0
13 458 Your Name (required) 5 0 input 2018-08-28T09:34:33Z 2018-08-28T09:34:38Z 5
14 458 Your Name (required) 5 0 input 2018-08-28T09:34:38Z 2018-08-28T09:34:40Z 2
15 458 Your Email (required) 6 0 input 2018-08-28T09:34:40Z 2018-08-28T09:34:52Z 12
16 458 Subject 7 0 input 2018-08-28T09:34:52Z 2018-08-28T09:34:52Z 0
17 458 Your Email (required) 6 0 input 2018-08-28T09:34:52Z 2018-08-28T09:34:57Z 5
18 458 Your Message 8 0 textarea 2018-08-28T09:34:57Z 2018-08-28T09:34:57Z 0
19 458 Subject 7 0 input 2018-08-28T09:34:57Z 0
答案 0 :(得分：1)
您正在寻找LEAD函数，但MySQL 5.6不支持该函数
因此，您可以尝试编写一个子查询来实现它。
模式（MySQL v8.0）
CREATE TABLE `form_events` (
`id` int(10) UNSIGNED NOT NULL,
`visitor_id` int(10) UNSIGNED NOT NULL,
`page_url` text COLLATE utf8mb4_unicode_ci NOT NULL,
`form_unique_identifier` varchar(255) COLLATE utf8mb4_unicode_ci NOT NULL,
`form_step_num` int(10) UNSIGNED NOT NULL,
`field_number` int(10) UNSIGNED NOT NULL,
`form_method` varchar(100) COLLATE utf8mb4_unicode_ci NOT NULL,
`form_action` text COLLATE utf8mb4_unicode_ci NOT NULL,
`form_css_id` text COLLATE utf8mb4_unicode_ci,
`form_css_class` text COLLATE utf8mb4_unicode_ci,
`field_label` text COLLATE utf8mb4_unicode_ci,
`field_type` varchar(50) COLLATE utf8mb4_unicode_ci NOT NULL,
`field_css_id` text COLLATE utf8mb4_unicode_ci,
`field_name` text COLLATE utf8mb4_unicode_ci,
`field_css_class` text COLLATE utf8mb4_unicode_ci,
`event_name` varchar(100) COLLATE utf8mb4_unicode_ci NOT NULL,
`event_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`created_at` timestamp NULL DEFAULT NULL,
`updated_at` timestamp NULL DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
--
-- Dumping data for table `form_events`
--
INSERT INTO `form_events` (`id`, `visitor_id`, `page_url`, `form_unique_identifier`, `form_step_num`, `field_number`, `form_method`, `form_action`, `form_css_id`, `form_css_class`, `field_label`, `field_type`, `field_css_id`, `field_name`, `field_css_class`, `event_name`, `event_time`, `created_at`, `updated_at`) VALUES
(1, 455, 'http://test.com/', 'FA67841442', 1, 5, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Name (required)\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text wpcf7-validates-as-required', 'click', '2018-08-28 08:14:00', '2018-08-28 08:14:03', '2018-08-28 08:14:03'),
(2, 455, 'http://test.com/', 'FA67841442', 1, 6, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Email (required)\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text wpcf7-email wpcf7-validates-as-required wpcf7-validates-as-email', 'select', '2018-08-28 08:14:03', '2018-08-28 08:14:06', '2018-08-28 08:14:06'),
(3, 455, 'http://test.com/', 'FA67841442', 1, 6, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Email (required)\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text wpcf7-email wpcf7-validates-as-required wpcf7-validates-as-email', 'select', '2018-08-28 08:14:06', '2018-08-28 08:14:06', '2018-08-28 08:14:06'),
(4, 455, 'http://test.com/', 'FA67841442', 1, 5, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Name (required)\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text wpcf7-validates-as-required', 'change', '2018-08-28 08:14:03', '2018-08-28 08:14:07', '2018-08-28 08:14:07'),
(5, 455, 'http://test.com/', 'FA67841442', 1, 7, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Subject\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text', 'click', '2018-08-28 08:14:10', '2018-08-28 08:14:13', '2018-08-28 08:14:13'),
(6, 455, 'http://test.com/', 'FA67841442', 1, 6, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Email (required)\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text wpcf7-email wpcf7-validates-as-required wpcf7-validates-as-email', 'change', '2018-08-28 08:14:10', '2018-08-28 08:14:13', '2018-08-28 08:14:13'),
(7, 455, 'http://test.com/', 'FA67841442', 1, 7, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Subject\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text', 'change', '2018-08-28 08:14:13', '2018-08-28 08:14:17', '2018-08-28 08:14:17'),
(8, 455, 'http://test.com/', 'FA67841442', 1, 0, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', 'form', 'form', '', NULL, 'wpcf7-form', 'submit', '2018-08-28 08:14:15', '2018-08-28 08:14:17', '2018-08-28 08:14:17'),
(9, 455, 'http://test.com/', 'FA67841442', 1, 8, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Message\n ', 'textarea', '', NULL, 'wpcf7-form-control wpcf7-textarea', 'select', '2018-08-28 08:14:13', '2018-08-28 08:14:17', '2018-08-28 08:14:17'),
(10, 455, 'http://test.com/', 'FA67841442', 1, 8, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Message\n ', 'textarea', '', NULL, 'wpcf7-form-control wpcf7-textarea', 'select', '2018-08-28 08:14:13', '2018-08-28 08:14:17', '2018-08-28 08:14:17'),
(11, 455, 'http://test.com/', 'FA67841442', 1, 8, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Message\n scdcscd ', 'textarea', '', NULL, 'wpcf7-form-control wpcf7-textarea', 'change', '2018-08-28 08:14:15', '2018-08-28 08:14:17', '2018-08-28 08:14:17'),
(13, 458, 'http://test.com/', 'FA67841442', 0, 5, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Name (required)\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text wpcf7-validates-as-required', 'click', '2018-08-28 09:34:33', '2018-08-28 09:34:36', '2018-08-28 09:34:36'),
(14, 458, 'http://test.com/', 'FA67841442', 0, 5, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Name (required)\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text wpcf7-validates-as-required', 'change', '2018-08-28 09:34:38', '2018-08-28 09:34:39', '2018-08-28 09:34:39'),
(15, 458, 'http://test.com/', 'FA67841442', 0, 6, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Email (required)\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text wpcf7-email wpcf7-validates-as-required wpcf7-validates-as-email', 'click', '2018-08-28 09:34:40', '2018-08-28 09:34:43', '2018-08-28 09:34:43'),
(16, 458, 'http://test.com/', 'FA67841442', 0, 7, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Subject\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text', 'click', '2018-08-28 09:34:52', '2018-08-28 09:34:55', '2018-08-28 09:34:55'),
(17, 458, 'http://test.com/', 'FA67841442', 0, 6, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Email (required)\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text wpcf7-email wpcf7-validates-as-required wpcf7-validates-as-email', 'change', '2018-08-28 09:34:52', '2018-08-28 09:34:56', '2018-08-28 09:34:56'),
(18, 458, 'http://test.com/', 'FA67841442', 0, 8, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Message\n ', 'textarea', '', NULL, 'wpcf7-form-control wpcf7-textarea', 'click', '2018-08-28 09:34:57', '2018-08-28 09:34:59', '2018-08-28 09:34:59'),
(19, 458, 'http://test.com/', 'FA67841442', 0, 7, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Subject\n ', 'input', '', NULL, 'wpcf7-form-control wpcf7-text', 'change', '2018-08-28 09:34:57', '2018-08-28 09:34:59', '2018-08-28 09:34:59'),
(20, 458, 'http://test.com/', 'FA67841442', 0, 8, 'post', 'http://test.com/#wpcf7-f9-p10-o1', '', 'wpcf7-form', ' Your Message\n ', 'textarea', '', NULL, 'wpcf7-form-control wpcf7-textarea', 'change', '2018-08-28 09:35:01', '2018-08-28 09:35:03', '2018-08-28 09:35:03');
查询＃1
SELECT *, coalesce(event_timeB - A.event_time,0) as timediff
FROM (
SELECT
A.id,
A.visitor_id,
A.field_label,
A.field_number,
A.form_step_num,
A.field_type,
A.event_time,
(
SELECT B.event_time
FROM form_events B
WHERE
A.visitor_id = B.visitor_id
AND
A.form_unique_identifier = B.form_unique_identifier
AND
A.event_time <= B.event_time
AND
(A.ID < B.ID OR A.event_time < B.event_time )
ORDER BY B.event_time
LIMIT 1
) event_timeB
FROM form_events A
)A
ORDER BY A.event_time ASC
结果
id visitor_id field_label field_number form_step_num field_type event_time event_time timediff
1 455 Your Name (required) 5 1 input 2018-08-28T08:14:00Z 2018-08-28T08:14:03Z 3
2 455 Your Email (required) 6 1 input 2018-08-28T08:14:03Z 2018-08-28T08:14:03Z 0
4 455 Your Name (required) 5 1 input 2018-08-28T08:14:03Z 2018-08-28T08:14:06Z 3
3 455 Your Email (required) 6 1 input 2018-08-28T08:14:06Z 2018-08-28T08:14:10Z 4
5 455 Subject 7 1 input 2018-08-28T08:14:10Z 2018-08-28T08:14:10Z 0
6 455 Your Email (required) 6 1 input 2018-08-28T08:14:10Z 2018-08-28T08:14:13Z 3
7 455 Subject 7 1 input 2018-08-28T08:14:13Z 2018-08-28T08:14:13Z 0
9 455 Your Message 8 1 textarea 2018-08-28T08:14:13Z 2018-08-28T08:14:13Z 0
10 455 Your Message 8 1 textarea 2018-08-28T08:14:13Z 2018-08-28T08:14:15Z 2
8 455 form 0 1 form 2018-08-28T08:14:15Z 0
13 458 Your Name (required) 5 0 input 2018-08-28T09:34:33Z 2018-08-28T09:34:38Z 5
14 458 Your Name (required) 5 0 input 2018-08-28T09:34:38Z 2018-08-28T09:34:40Z 2
15 458 Your Email (required) 6 0 input 2018-08-28T09:34:40Z 2018-08-28T09:34:52Z 12
16 458 Subject 7 0 input 2018-08-28T09:34:52Z 2018-08-28T09:34:52Z 0
17 458 Your Email (required) 6 0 input 2018-08-28T09:34:52Z 2018-08-28T09:34:57Z 5
18 458 Your Message 8 0 textarea 2018-08-28T09:34:57Z 2018-08-28T09:34:57Z 0
19 458 Subject 7 0 input 2018-08-28T09:34:57Z 0
答案 1 :(得分：0)
唯一的问题，这将输出不需要的2列。
SELECT
A.id, A.visitor_id, A.field_label, A.field_number, A.form_step_num, A.field_type, A.event_time,
case when @visitor_id <> visitor_id then @time := event_time end,
@visitor_id := visitor_id,
event_time - @time as timediff
FROM form_events A, (select @visitor_id := 0, @time := 0) t
ORDER BY a.visitor_id, A.event_time ASC