Question

如何从每个表中提取每天的FIRST'StartAddress'。

结果必须如下所示。

+------------+---------------+--------------------+--------------------+
| Date       | SamplingStart | StartAddress       | StopAddress        |
+------------+---------------+--------------------+--------------------+
| 2016-02-22 | 08:00:00      | 26 Riverside Drive | 70 Piet Retief     |
| 2016-02-23 | 05:15:00      | Balizza            | Mars               |
+------------+---------------+--------------------+--------------------|

表：

+------------+---------------+--------------------+--------------------+
| Date       | SamplingStart | StartAddress       | StopAddress        |
+------------+---------------+--------------------+--------------------+
| 2016-02-22 | 08:00:00      | 26 Riverside Drive | 70 Piet Retief     |
| 2016-02-22 | 09:00:00      | 10 Glen Drive      | 16 Olga Street     |
| 2016-02-22 | 10:00:00      | 66 Bremerhof       | 26 Bluewater Drive |
| 2016-02-22 | 11:00:00      | 7 New Street       | Walker Drive       |
| 2016-02-22 | 13:00:00      | Goodwood Street    | Blouberg           |
| 2016-02-22 | 15:00:00      | Marine Drive       | William Moffet     |
| 2016-02-22 | 18:00:00      | Jumanji            | Paterson           |
| 2016-02-23 | 07:00:00      | 25 Eazi Street     | 70 Kings Street    |
| 2016-02-23 | 07:20:00      | Cool Blue          | Pick n Pay         |
| 2016-02-23 | 05:15:00      | Balizza            | Mars               |
| 2016-02-23 | 20:15:00      | Neverland          | Club Shakes        |
| 2016-02-23 | 23:15:00      | Castros            | Stones             |
| 2016-02-23 | 14:45:00      | Seagate            | Ermelo             |
| 2016-02-23 | 16:30:00      | Mafikeng           | Goodwood           |
+------------+---------------+--------------------+--------------------+

Answer 1

试试这个：

SELECT 
    * 
FROM
    tbl
WHERE 
    (Date, SamplingStart) IN
    (
        SELECT tbl2.Date, MIN(tbl2.SamplingStart)
        FROM tbl tbl2
        WHERE tbl.Date = tbl2.Date
    );

Answer 2

您可以通过为每个日期添加行号来实现此目的。

<强>查询

select t.`Date`, t.SamplingStart, t.StartAddress, t.StopAddress from
(
    select `Date`,SamplingStart, StartAddress, StopAddress, 
    (
        case `Date` when @curA 
        then @curRow := @curRow + 1 
        else @curRow := 1 and @curA := `Date` end 
    ) as rn 
    from your_table_name t, 
    (select @curRow := 0, @curA := '') r 
    order by `Date`, SamplingStart
)t
where t.rn = 1;

SQL Fiddle demo

Answer 3

您可以使用NOT EXISTS（）

SELECT t.*
FROM YourTable t
WHERE NOT EXISTS(SELECT 1 FROM YourTable s
                 WHERE t.date = s.date 
                   and t.SamplingStart > s.SamplingStart)

Answer 4

Select Date, MIN(SamplingStart) AS SamplingStart, StartAddress, StopAddress
from Table Group By Date;

MYSQL：如何从表中提取以下数据？

4 个答案: