Question

我有一张如下表：

    +-------------+--------------+
    | current_day | browser      |
    +-------------+--------------+
    | 2016-05-02  | Safari       |
    | 2016-05-03  | Safari       |
    | 2016-05-04  | Safari       |
    | 2016-05-05  | Safari       |
    | 2016-05-06  | Safari       |
    | 2016-05-07  | Safari       |
    | 2016-05-08  | Safari       |
    | 2016-05-09  | Opera        |
    | 2016-05-10  | Opera        |
    | 2016-05-11  | Opera        |
    | 2016-05-12  | Opera        |
    | 2016-05-13  | Opera        |
    | 2016-05-14  | Opera        |
    | 2016-05-15  | Chrome       |
    | 2016-05-16  | Firefox      |
    | 2016-05-17  | Firefox      |
    | 2016-05-18  | Firefox      |
    | 2016-05-19  | Firefox      |
    | 2016-05-20  | Firefox      |
    | 2016-05-21  | Firefox      |
    | 2016-05-22  | Firefox      |
    | 2016-05-23  | Safari       |
    | 2016-05-24  | Safari       |
    | 2016-05-25  | Safari       |
    | 2016-05-26  | Safari       |
    | 2016-05-27  | Safari       |
    | 2016-05-28  | Safari       |
    | 2016-05-29  | Safari       |
    | 2016-05-30  | Opera        |
    | 2016-05-31  | Opera        |
    | 2016-06-01  | Opera        |
    | 2016-06-02  | Firefox      |
    | 2016-06-03  | Firefox      |
    | 2016-06-04  | Firefox      |
    | 2016-06-05  | Firefox      |
    | 2016-06-06  | Firefox      |
    | 2016-06-07  | Firefox      |
    | 2016-06-08  | Firefox      |
    | 2016-06-09  | Chrome       |
    | 2016-06-10  | Chrome       |
    | 2016-06-11  | Chrome       |
    | 2016-06-12  | Chrome       |
    | 2016-06-13  | Chrome       |
    | 2016-06-14  | Chrome       |
    | 2016-06-15  | Chrome       |
    | 2016-06-16  | Chrome       |
    +-------------+--------------+

我想在“浏览器”中提取每个序列的第一个和最后一个序列。列，换句话说，结果如下：

    +-------------+--------------+
    | current_day | browser      |
    +-------------+--------------+
    | 2016-05-02  | Safari       |
    | 2016-05-08  | Safari       |
    | 2016-05-09  | Opera        |
    | 2016-05-14  | Opera        |
    | 2016-05-15  | Chrome       |
    | 2016-05-16  | Firefox      |
    | 2016-05-22  | Firefox      |
    | 2016-05-23  | Safari       |
    | 2016-05-29  | Safari       |
    | 2016-05-30  | Opera        |
    | 2016-06-01  | Opera        |
    | 2016-06-02  | Firefox      |
    | 2016-06-08  | Firefox      |
    | 2016-06-09  | Chrome       |
    | 2016-06-16  | Chrome       |
    +-------------+--------------+

创建MYSQL查询是否可行/方便？或者更好地提取所有结果并使用php执行一些后期处理？

Answer 1

您可以使用以下查询：

SELECT MIN(current_day) AS start_day, 
       MAX(current_day) AS stop_day, 
       browser
FROM (
   SELECT current_day, browser,
          @grp := IF(@br = browser, @grp,
                     IF(@br := browser, @grp+1, @grp+1)) AS grp
   FROM mytable 
   CROSS JOIN (SELECT @grp := 0, @br := '') AS vars
   ORDER BY current_day) AS t
GROUP BY browser, grp

上述查询使用变量，以便识别具有相同browser值的连续记录的孤岛。它为每个浏览器返回一行。您必须重复相同的子查询两次并使用UNION，如果您想为每个最小/最大日期获得两个单独的行。

Demo here

Answer 2

试试这个：

SELECT current_day, browser
FROM table_name AS a
WHERE current_day = (
    SELECT MAX(current_day)
    FROM table_name AS b
    WHERE a.browser = b.browser
) 
OR current_day = (
    SELECT MIN(current_day)
    FROM table_name AS c
    WHERE a.browser = c.browser
)

方法稍微简单：

select min(current_day), max(current_day), browser from test group by browser;

Answer 3

这里有2个样本，每个浏览器一行和两行

一行

SELECT
  min(current_day) AS  start_date
  , max(current_day) AS end_date
  , browser
FROM your_table
GROUP BY browser;

两行

SELECT * FROM (
  SELECT
    min(current_day)
    , browser
  FROM your_table
  UNION ALL
  SELECT
    max(current_day)
    , browser
  FROM your_table
)
ORDER BY broser,current_day;

Answer 4

试试这个

SELECT r.* FROM (SELECT t.* FROM (SELECT k.* FROM (SELECT * FROM `tbl_test` ORDER BY `current_day` DESC) as k GROUP BY k.browser) as t  UNION SELECT h.* FROM (SELECT q.* FROM (SELECT * FROM `tbl_test` ORDER BY `current_day` ASC) as q GROUP BY k.browser) as h ) as r ORDER BY r.current_day

mysql：按第一个和最后一个出现的组

4 个答案: