Question

我是存储过程的新手，所以我可能做错了。我创建了一个存储过程，该存储过程可以带回月份名称，月份开始日期和月份结束，但是我得到了12个独立的数据集。

如何将其组合成一个？

BEGIN

SET @i = 0;
SET @start_date = "2018-09-01";
SET @end_date = LAST_DAY('2018-09-01');

WHILE @i < 12 DO
     
    SELECT MONTHNAME(@start_date) AS month, @start_date, @end_date;
    
    SET @i = @i + 1;
    SET @start_date = DATE_ADD(@start_date, INTERVAL 1 MONTH);
    SET @end_date = LAST_DAY(DATE_ADD(@end_date, INTERVAL 1 MONTH));
 
END WHILE;

END

Answer 1

您不需要存储过程。

set @start_date = '2018-09-01';
with recursive months(m) as (
  select 0
  union all
  select m + 1
  from months
  where m < 11
)
select @start_date + interval m.m month as first_day
     , last_day(@start_date + interval m.m month) as last_day
from months m
order by m.m asc

结果：

first_day   last_day
2018-09-01  2018-09-30
2018-10-01  2018-10-31
2018-11-01  2018-11-30
2018-12-01  2018-12-31
2019-01-01  2019-01-31
2019-02-01  2019-02-28
2019-03-01  2019-03-31
2019-04-01  2019-04-30
2019-05-01  2019-05-31
2019-06-01  2019-06-30
2019-07-01  2019-07-31
2019-08-01  2019-08-31

但是您当然也可以在SP中使用该查询。

Answer 2

重写@Paul Spiegel查询，以便我了解递归查询的工作原理。

SET @start = "2018-09-01";

WITH RECURSIVE months (m) 
AS (
      SELECT 0
      UNION ALL
      SELECT m + 1 
      FROM months 
      WHERE m < 12
    )
SELECT
MONTHNAME(DATE_ADD(@start, INTERVAL m MONTH)) AS month_name,
CONCAT(DATE_ADD(@start, INTERVAL m MONTH), " 00:00:00") AS start_of_month,
CONCAT(LAST_DAY(DATE_ADD(@start, INTERVAL m MONTH)), " 23:59:59") AS end_of_month
FROM months;

Answer 3

对于8.0之前的MySQL版本，我们可以执行以下操作：

SELECT MONTHNAME(d.dt + INTERVAL i.n MONTH)  AS month
     , d.dt + INTERVAL i.n MONTH             AS start_date
     , LAST_DAY(d.dt + INTERVAL i.n MONTH)   AS end_date
  FROM ( SELECT '2018-09-01' + INTERVAL 0 MONTH AS dt ) d
 CROSS
  JOIN ( SELECT 0 AS n UNION ALL SELECT 1 UNION ALL SELECT 2
         UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5
         UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8
         UNION ALL SELECT 9 UNION ALL SELECT 10 UNION ALL SELECT 11
       ) i
 ORDER
    BY i.n

MySQL存储过程，while循环，联合数据集

3 个答案: