[英]Select the last position of the same row in MySQL
The version of MySQL database is 5.5.62 MySQL数据库版本为5.5.62
This is my table这是我的桌子
+-----+---------------------+----------+--------------+
| sId | sDateHour | sElement | sStatus |
+-----+---------------------+----------+--------------+
| 1 | 2020-01-01 01:54:40 | 044572 | Registered |
| 2 | 2020-01-01 02:02:11 | 035219 | Unregistered |
| 3 | 2020-01-01 02:36:01 | 044572 | Unregistered |
| 4 | 2020-01-01 02:36:06 | 020523 | Registered |
| 5 | 2020-01-01 02:36:15 | 020523 | Unregistered |
| 6 | 2020-01-01 03:05:22 | 065164 | Unregistered |
| 7 | 2020-01-01 03:05:51 | 086113 | Registered |
| 8 | 2020-01-01 03:49:09 | 086113 | Unregistered |
| 9 | 2020-01-01 03:58:58 | 070328 | Unregistered |
| 10 | 2020-01-01 04:15:15 | 065570 | Unregistered |
| 11 | 2020-01-01 04:27:29 | 045473 | Registered |
| 12 | 2020-01-01 04:40:36 | 074000 | Unregistered |
| 13 | 2020-01-01 04:40:43 | 045473 | Unregistered |
| 14 | 2020-01-01 05:00:50 | 070245 | Unregistered |
| 15 | 2020-01-01 06:17:53 | 079107 | Registered |
+-----+---------------------+----------+--------------+
i need to select the last position (field sDateHour
) of the same row value sElement
when the sStatus
value is Unregistered
当
sStatus
值Unregistered
时,我需要 select 相同行值sElement
的最后一个 position (字段sDateHour
)
i need this return我需要这个回报
+-----+---------------------+----------+--------------+
| sId | sDateHour | sElement | sStatus |
+-----+---------------------+----------+--------------+
| 2 | 2020-01-01 02:02:11 | 035219 | Unregistered |
| 3 | 2020-01-01 02:36:01 | 044572 | Unregistered |
| 5 | 2020-01-01 02:36:15 | 020523 | Unregistered |
| 6 | 2020-01-01 03:05:22 | 065164 | Unregistered |
| 8 | 2020-01-01 03:49:09 | 086113 | Unregistered |
| 9 | 2020-01-01 03:58:58 | 070328 | Unregistered |
| 10 | 2020-01-01 04:15:15 | 065570 | Unregistered |
| 12 | 2020-01-01 04:40:36 | 074000 | Unregistered |
| 13 | 2020-01-01 04:40:43 | 045473 | Unregistered |
| 14 | 2020-01-01 05:00:50 | 070245 | Unregistered |
+-----+---------------------+----------+--------------+
eg例如
In this case in table i have the same element 044572
value在这种情况下,在表中我有相同的元素
044572
值
+-----+---------------------+----------+--------------+
| sId | sDateHour | sElement | sStatus |
+-----+---------------------+----------+--------------+
| 1 | 2020-01-01 01:54:40 | 044572 | Registered |
| 3 | 2020-01-01 02:36:01 | 044572 | Unregistered |
+-----+---------------------+----------+--------------+
the sId
number no. sId
编号。 3 is newer (last position) than sId
no. 3 比
sId
no 更新(最后位置)。 1 and the value of sElement
is Unregistered
1 且
sElement
的值为Unregistered
i need extract this row我需要提取这一行
And I have tried this solution without success because the set is empty我试过这个解决方案没有成功,因为集合是空的
mysql> SELECT
*
FROM
`tbl_elements` A
INNER JOIN (
SELECT
sStatus,
sElement,
MAX(sDateHour) LastDatetimeForElements
FROM
`tbl_elements`
WHERE
sStatus = 'Unregistered'
) B ON A.sElement = B.sElement
AND A.sDateHour = B.LastDatetimeForElements;
Empty set
How to do resolve this?如何解决这个问题?
Please, any suggestion...请问有什么建议...
My table below我下面的表
-- ----------------------------
-- Table structure for tbl_elements
-- ----------------------------
DROP TABLE IF EXISTS `tbl_elements`;
CREATE TABLE `tbl_elements` (
`sId` int(11) NOT NULL AUTO_INCREMENT,
`sDateHour` datetime DEFAULT NULL,
`sElement` varchar(255) DEFAULT NULL,
`sStatus` varchar(255) DEFAULT NULL,
PRIMARY KEY (`sId`)
) ENGINE=InnoDB AUTO_INCREMENT=16 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of tbl_elements
-- ----------------------------
INSERT INTO `tbl_elements` VALUES ('1', '2020-01-01 01:54:40', '044572', 'Registered');
INSERT INTO `tbl_elements` VALUES ('2', '2020-01-01 02:02:11', '035219', 'Unregistered');
INSERT INTO `tbl_elements` VALUES ('3', '2020-01-01 02:36:01', '044572', 'Unregistered');
INSERT INTO `tbl_elements` VALUES ('4', '2020-01-01 02:36:06', '020523', 'Registered');
INSERT INTO `tbl_elements` VALUES ('5', '2020-01-01 02:36:15', '020523', 'Unregistered');
INSERT INTO `tbl_elements` VALUES ('6', '2020-01-01 03:05:22', '065164', 'Unregistered');
INSERT INTO `tbl_elements` VALUES ('7', '2020-01-01 03:05:51', '086113', 'Registered');
INSERT INTO `tbl_elements` VALUES ('8', '2020-01-01 03:49:09', '086113', 'Unregistered');
INSERT INTO `tbl_elements` VALUES ('9', '2020-01-01 03:58:58', '070328', 'Unregistered');
INSERT INTO `tbl_elements` VALUES ('10', '2020-01-01 04:15:15', '065570', 'Unregistered');
INSERT INTO `tbl_elements` VALUES ('11', '2020-01-01 04:27:29', '045473', 'Registered');
INSERT INTO `tbl_elements` VALUES ('12', '2020-01-01 04:40:36', '074000', 'Unregistered');
INSERT INTO `tbl_elements` VALUES ('13', '2020-01-01 04:40:43', '045473', 'Unregistered');
INSERT INTO `tbl_elements` VALUES ('14', '2020-01-01 05:00:50', '070245', 'Unregistered');
INSERT INTO `tbl_elements` VALUES ('15', '2020-01-01 06:17:53', '079107', 'Registered');
Solution解决方案
You need GROUP BY sStatus, sElement你需要 GROUP BY sStatus, sElement
SELECT A.*
FROM `tbl_elements` A
INNER JOIN (
SELECT
sStatus,
sElement,
MAX(sDateHour) LastDatetimeForElements
FROM
`tbl_elements`
WHERE sStatus = 'Unregistered'
GROUP BY sStatus,
sElement,
) B ON A.sElement = B.sElement
AND A.sDateHour = B.LastDatetimeForElements
AND A.sStatus = B.sStatus
and the join on all the column for right matching并加入所有列以进行正确匹配
Use a correlated subquery which returns the max sDateHour
for each sElement
:使用一个相关的子查询,它返回每个
sElement
sDateHour
select t.*
from tbl_elements t
where t.sStatus = 'Unregistered'
and t.sDateHour = (select max(sDateHour) from tbl_elements where sElement = t.sElement and sStatus = t.sStatus)
See the demo .见演示。
Results:结果:
> sId | sDateHour | sElement | sStatus
> --: | :------------------ | :------- | :-----------
> 2 | 2020-01-01 02:02:11 | 035219 | Unregistered
> 3 | 2020-01-01 02:36:01 | 044572 | Unregistered
> 5 | 2020-01-01 02:36:15 | 020523 | Unregistered
> 6 | 2020-01-01 03:05:22 | 065164 | Unregistered
> 8 | 2020-01-01 03:49:09 | 086113 | Unregistered
> 9 | 2020-01-01 03:58:58 | 070328 | Unregistered
> 10 | 2020-01-01 04:15:15 | 065570 | Unregistered
> 12 | 2020-01-01 04:40:36 | 074000 | Unregistered
> 13 | 2020-01-01 04:40:43 | 045473 | Unregistered
> 14 | 2020-01-01 05:00:50 | 070245 | Unregistered
You need to add GROUP BY
for your inner query
您需要为您的
inner query
添加GROUP BY
SELECT
*
FROM
`tbl_elements` A
INNER JOIN (
SELECT
sStatus,
sElement,
MAX(sDateHour) LastDatetimeForElements
FROM
`tbl_elements`
WHERE
sStatus = 'Unregistered'
GROUP BY sStatus, sElement <----
) B ON A.sElement = B.sElement
AND A.sDateHour = B.LastDatetimeForElements;
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