mysql - 每列的 SQL 唯一值

Question

所以我试图从每一列中获取唯一的值。到目前为止我已经尝试过。

日期:周一、周二、周三、周四、周五

时间:上午 8 点至 10 点、下午 10 点至 12 点、下午 1 点至 3 点、下午 3 点至 5 点、下午 5 点至 7 点

SELECT DISTINCT Day, Time FROM table GROUP BY Day, Time;

示例:

Monday    8-10am
Monday    3-5pm
Monday    5-7pm
Tuesday   10-12pm
Tuesday   5-7pm
Wednesday 3-5pm
Thursday  10-12pm
Thursday   1-3pm
Friday    8-10am
Friday    1-3pm

这不会为我提供每列的唯一值，而是为一天中的每个时间提供唯一值。

SELECT
(SELECT group_concat(DISTINCT Day) FROM workingTimeDate) as Day,
(SELECT group_concat(DISTINCT Time) FROM workingTimeDate) as Time
FROM workingTimeDate;

这将给出:

Monday,Tuesday,Wednesday,Thursday,Friday   8-10am,10-12pm,1-3pm,3-5pm,5-7pm

这会将值分组为两列，但我希望它们位于单独的列中。

我想要的是

Day        Time
Monday     8-10am
Tuesday    10-12pm
Wednesday  1-3pm
Thursday   3-5pm
Friday     5-7pm

Answer 1

你可以这样做:

select distinct day, cast(NULL as time) from t
union all
select distinct cast(NULL as date), time from t;