如何合并没有空字段的行

Question

我还在学习 MySQL，我有这张表...

staff_id	Name	Monday	Tuesday
1	Mark	8:00am-5:00pm	9:00am-6:00pm
2	Steve	9:00am-6:00pm	7:00am-4:00pm

我已经设法使用下面的脚本将新行拆分并插入到同一个表中。

INSERT INTO table (staff_id,Name,Monday)
(SELECT staff_id, Name, "8:00am-1:00pm"
        FROM table
        WHERE Monday= "8:00am-5:00pm");

INSERT INTO table (staff_id,Name,Monday)
(SELECT staff_id, Name, "2:00pm-5:00pm"
        FROM table
        WHERE Monday= "8:00am-5:00pm");
...etc...

它有效，但我最终得到了太多行（我正在处理数千行）。
有没有一种方法可以让我只使用 MySQL 脚本来获得如下表格？

staff_id	Name	Monday	Tuesday
1	Mark	8:00am-1:00pm	9:00am-2:00pm
1	Mark	2:00pm-5:00pm	3:00pm-6:00pm
2	Steve	9:00am-2:00pm	7:00am-12:00pm
2	Steve	3:00pm-6:00pm	1:00pm-4:00pm

其他解决方案建议使用聚合函数 (MAX)，不幸的是，这在我的情况下不起作用，我不知道如何为此目的正确使用“JOIN”。
任何帮助将不胜感激。

Answer 1

你必须使用 UPDATE 而不是 INSERT INTO

CREATE TABLE mytable
    (`staff_id` int, `Name` varchar(5), `Monday` varchar(13), `Tuesday` varchar(13))
;
    
INSERT INTO mytable
    (`staff_id`, `Name`, `Monday`, `Tuesday`)
VALUES
    (1, 'Mark', '8:00am-5:00pm', '9:00am-6:00pm'),
    (2, 'Steve', '9:00am-6:00pm', '7:00am-4:00pm')
;

UPDATe mytable SET Monday = "8:00am-1:00pm"

        WHERE Monday= "8:00am-5:00pm";

UPDATe mytable SET Monday = "8:00am-1:00pm"

        WHERE Monday= "9:00am-6:00pm";

SELECT * FROM mytable

员工编号 |姓名 |星期一 |周二 --------: | :---- | :------------ | :------------ 1 |马克 |上午 8:00 至下午 1:00 |上午 9:00 至下午 6:00 2 |史蒂夫 |上午 8:00 至下午 1:00 |上午 7:00 至下午 4:00

db小提琴here