mysql - 有没有办法获得一个月的第一个和最后一个工作日？

Question

我想问一下在 MySQL 中是否有一种聪明或简单的方法来获取一个月的第一个和最后一个工作日。换句话说，我想避开周末并适本地转移第一天或最后一天。

例如:

For the period: 2011-05-01 till 2011-05-31
First weekday should be: 2011-05-02 and not 2011-05-01 as 2011-05-01 is Sunday.
Last weekday should be: 2011-05-31 as it is Tuesday.

For the period: 2011-04-01 till 2011-04-30,
First weekday: 2011-04-01
Last weekday: 2011-04-29

Answer 1

如何以 LAST_DAY() 的样式定义函数 FIRST_WDOM()(星期/月的工作日)和 LAST_WDOM() ？

DELIMITER //
CREATE FUNCTION first_wdom (d DATETIME) -- First work/week day of month
RETURNS DATE DETERMINISTIC
BEGIN
  DECLARE first_dom DATE;
  SET first_dom = DATE_FORMAT(d, '%Y-%m-01');

  RETURN first_dom + INTERVAL (CASE DAYOFWEEK(first_dom)
                               WHEN 1 THEN 1
                               WHEN 7 THEN 2
                               ELSE 0
                               END) DAY;
END //
CREATE FUNCTION last_wdom (d DATETIME) -- Last work/week day of month
RETURNS DATE DETERMINISTIC
BEGIN
  DECLARE last_dom DATE;
  SET last_dom = LAST_DAY(d);

  RETURN last_dom - INTERVAL (CASE DAYOFWEEK(last_dom)
                              WHEN 1 THEN 2
                              WHEN 7 THEN 1
                              ELSE 0
                              END) DAY;
END //
DELIMITER ;

mysql> SELECT FIRST_WDOM('2011-05-10'), LAST_WDOM('2011-05-10');
+--------------------------+-------------------------+
| FIRST_WDOM('2011-05-10') | LAST_WDOM('2011-05-10') |
+--------------------------+-------------------------+
| 2011-05-02               | 2011-05-31              | 
+--------------------------+-------------------------+
1 row in set (0.01 sec)

这只是对 ic3b3rg's answer 的改编，并假设周六和周日是您的周末。我使用 DATETIME 而不是 DATE 作为输入类型，以避免在传入时出现截断警告，例如 NOW()。