Question

如何从包含两个日期列的表中计算每月唯一天数，其中期间可能有间隙和重叠？

我宁愿不使用日历表来获取独特的日子，因为它会生成一个包含数千条记录的临时表，并且资源有限。

示例表：

+---------+------------+------------+
| mygroup | alpha      | omega      |
+---------+------------+------------+
|       1 | 2017-02-04 | 2017-04-14 |
|       1 | 2017-03-25 | 2017-03-28 |
|       1 | 2017-01-23 | 2017-01-25 |
|       2 | 2017-02-05 | 2017-02-20 |
|       1 | 2017-04-28 | 2017-05-12 |
|   etc.  |    etc.    |    etc.    |
+---------+------------+------------+

Answer 1

这是你需要的吗？

select count(distinct selected_date),te.mygroup, MONTHNAME(selected_date)from 
(select adddate('1970-01-01',t4.i*10000 + t3.i*1000 + t2.i*100 + t1.i*10 + t0.i) selected_date from
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t0,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t1,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t2,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t3,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t4) v
 cross join test te  
where selected_date between te.alpha and te.omega
group by mygroup, MONTHNAME(selected_date)

Оutput为您的例子：

'17','1','April'
'25','1','February'
'3','1','January'
'31','1','March'
'12','1','May'
'16','2','February'

计数可能大于每月的天数，因为这样的重叠存在于几行中 - 这不是错误。

Answer 2

还有另一种方法可以比日历表快10倍。

最大的资源扰流器是日历表本身，它用于过滤独特的日子。但是，不是使用整个表记录，而是可以使用UINT中的31位来完成。

Recepe：

创建仅包含月份的日历表
以月为单位剪切期间，并将其与日历表相结合
将句点翻译为UINT的位数
OR每月UINTs的唯一性
将他们的位数计算为每月唯一的天数

输出：

+--------------+---------+---------+-------+
| Period       | Group 1 | Group 2 | Total |
+--------------+---------+---------+-------+
| 2017 month 5 |      11 |       0 |    11 |
| 2017 month 4 |      15 |       0 |    15 |
| 2017 month 3 |      30 |       0 |    30 |
| 2017 month 2 |      24 |      15 |    39 |
| 2017 month 1 |       2 |       0 |     2 |
+--------------+---------+---------+-------+

MySQL查询：

SELECT
  `tabulate`.`period` AS `Period`,
  SUM(IF(`tabulate`.`mygroup` = 1,            
    `tabulate`.`days`, 0)) AS `Group 1`,
  SUM(IF(`tabulate`.`mygroup` = 2,             
    `tabulate`.`days`, 0)) AS `Group 2`,
  SUM(`tabulate`.`days`) AS `Total`
FROM
  ( SELECT
      `unique`.`period`,
      BIT_COUNT(BIT_OR(CONV(CONCAT(
        REPEAT("1", DAYOFMONTH(`unique`.`omega`) - DAYOFMONTH(`unique`.`alpha`)),
        REPEAT("0", DAYOFMONTH(`unique`.`alpha`) - 1)
      ), 2, 10))) AS `days`,
      `unique`.`mygroup`
    FROM
      ( SELECT
          DATE_FORMAT(`permonth`.`period_alpha`, "%Y month %c") AS `period`,
          GREATEST(`permonth`.`period_alpha`, `permonth`.`example_alpha`) AS `alpha`,
          LEAST(`permonth`.`period_omega`, `permonth`.`example_omega`) AS `omega`,
          `permonth`.`mygroup`
        FROM 
          ( SELECT
              `period`.`alpha` AS `period_alpha`,
              DATE_SUB(`period`.`omega`, INTERVAL 1 DAY) AS `period_omega`,
              `example`.`mygroup`,
              IFNULL(`example`.`alpha`, `period`.`alpha`) AS `example_alpha`,
              IFNULL(`example`.`omega`, CURDATE()) AS `example_omega`
            FROM
              ( SELECT
                  DATE_ADD(
                    MAKEDATE(YEAR(CURDATE()), 1),
                    INTERVAL `season`.`n` + (`month`.`n` << 2) MONTH
                  ) AS `alpha`,
                  DATE_ADD(
                    MAKEDATE(YEAR(CURDATE()), 1),
                    INTERVAL 1 + `season`.`n` + (`month`.`n` << 2) MONTH
                  ) AS `omega`
                FROM
                  (           SELECT 0 AS `n`
                    UNION ALL SELECT 1
                    UNION ALL SELECT 2
                  ) AS `month`
                  CROSS JOIN (SELECT 0 AS `n`
                    UNION ALL SELECT 1
                    UNION ALL SELECT 2
                    UNION ALL SELECT 3  
                  ) AS `season`
              ) AS `period`
              INNER JOIN 
                ( SELECT 1 AS `mygroup`, "2017-02-04" AS `alpha`, "2017-04-14" AS `omega`
                  UNION ALL SELECT 1, "2017-03-25", "2017-03-28"
                  UNION ALL SELECT 1, "2017-01-23", "2017-01-25"
                  UNION ALL SELECT 2, "2017-02-05", "2017-02-20"
                  UNION ALL SELECT 1, "2017-04-28", "2017-05-12"
                ) AS `example` ON (
                  (`example`.`alpha` < `period`.`omega` OR `example`.`alpha` IS NULL)
                  AND IFNULL(`example`.`omega`, CURDATE()) >= `period`.`alpha`
                )
          ) AS `permonth`
      ) AS `unique`
    GROUP BY
      `unique`.`period`,
      `unique`.`mygroup`
  ) AS `tabulate`
GROUP BY `tabulate`.`period`
ORDER BY `tabulate`.`period` DESC

MySQL：计算具有重叠和间隙的独特日期（优化）

2 个答案: