如何定义功能FIRST_WDOM()（星期/一个月的工作日）并LAST_WDOM()采用样式LAST_DAY()？
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ic3b3rg答案的改编，并假定星期六和星期日为您的周末。我使用DATETIME而不是DATE作为输入类型，以避免传入时出现截断警告Now()。
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