mysql:檢查表是否存在時間重叠？

這是我很多年前找到答案的查詢模式：

SELECT *
FROM mytable a
JOIN mytable b on a.starttime <= b.endtime
    and a.endtime >= b.starttime
    and a.name != b.name; -- ideally, this would compare a "key" column, eg id

要查詢"任何重叠"，您可以將時間範圍的相反两端相互比较.我不得不掏出笔和纸，画出相邻的範圍，以了解邊缘情况归結為這種比较。

---

如果要防止任何行重叠，請在觸發器中放置此查詢的變體：

create trigger mytable_no_overlap
before insert on mytable
for each row
begin
  if exists (select * from mytable
             where starttime <= new.endtime
             and endtime >= new.starttime) then
    signal sqlstate '45000' SET MESSAGE_TEXT = 'Overlaps with existing data';
  end if;
end;

我想要一个通用函式来檢查几天的两个時間範圍是否重叠，這在時間表開始於午夜之前和結束之後（例如" 17：00：00-03：00： 00"和" 14：00：00-01：00：00"應该重叠，因此我修改了波西米亚风格的解決方案

您可以按以下方式使用此功能

SELECT func_time_overlap("17:00:00","03:00:00", "14:00:00","01:00:00")

或者像您這樣的情况

SELECT *
FROM mytable a
JOIN mytable b ON (
    a.name != b.name 
    AND func_time_overlap(a.starttime, a.endtime, b.starttime, b.endtime)
);

這是函式定義

CREATE FUNCTION `func_time_overlap`(a_start TIME, a_end TIME, b_start TIME, b_end TIME) 
RETURNS tinyint(1) 
DETERMINISTIC
BEGIN
-- there are only two cases when they don't overlap, but a lot of possible cases where they do overlap
-- There are two time formats, one is an interval of time that can go over 24 hours, the other is a daily time format that never goes above 24 hours
-- by default mysql uses TIME as an interval
-- this converts a TIME interval into a date time format
-- I'm not using `TIME(CAST(a_start AS DATETIME));` to convert the time interval to a time
-- because it uses the current day by default and might get affected by the timezone settings of the database, 
-- just imagine the next day having the DST change.
-- although the CAST should work fine if you use UTC
IF a_start >= 24 THEN 
    SET a_start = TIME(CONCAT(MOD(HOUR(a_start), 24),':',MINUTE(a_start),':',SECOND(a_start))); 
END IF;
IF b_start >= 24 THEN 
    SET b_start = TIME(CONCAT(MOD(HOUR(b_start), 24),':',MINUTE(b_start),':',SECOND(b_start))); 
END IF;
IF a_end > 24 THEN 
    SET a_end = TIME(CONCAT(MOD(HOUR(a_end), 24),':',MINUTE(a_end),':',SECOND(a_end))); 
END IF;
IF b_end > 24 THEN 
    SET b_end = TIME(CONCAT(MOD(HOUR(b_end), 24),':',MINUTE(b_end),':',SECOND(b_end))); 
END IF;

-- if the time range passes the midnight mark, then add 24 hours to the time
IF a_start >= a_end THEN 
    SET a_end = a_end + INTERVAL 24 HOUR; 
END IF;
IF b_start >= b_end THEN 
    SET b_end = b_end + INTERVAL 24 HOUR; 
END IF;
RETURN a_start < b_end AND a_end > b_start;

END

我不使用 TIME(CAST(a_start AS DATETIME)); 將時間間隔轉換為時間，因為預設情况下它使用的是当前日期，並且可能会受到資料庫時區設置的影响，請想象第二天DST發生了變化。

如果您的資料庫正在使用UTC時區（應使用），則可以使用此

IF a_start >= 24 THEN 
    SET a_start = TIME(CAST(a_start AS DATETIME)); 
END IF;
IF b_start >= 24 THEN 
    SET b_start = TIME(CAST(b_start AS DATETIME)); 
END IF;
IF a_end > 24 THEN 
    SET a_end = TIME(CAST(a_end AS DATETIME));
END IF;
IF b_end > 24 THEN 
    SET b_end = TIME(CAST(b_end AS DATETIME));
END IF;

尝試一下：

declare @tempTbl table(RecID)
    insert into @tempTbl
    Select RecID
    from 
    (
    Select t.RecID from Table1 t,Table1 t1
    where t.StartTime between t1.StartTime AND t1.EndTime
    AND t.RecID <> t1.RecID  
    )

尝試一下，它對我有用

SELECT * from Shedulles a 
where exists 
( select 1 from Shedulles b 
    where 
    a.ShedulleId != b.ShedulleId 
    and ( a.DateFrom between b.DateFrom and b.DateTo 
    or a.DateTo between b.DateFrom and b.DateTo 
    or b.DateFrom between a.DateFrom and a.DateTo ) 
    and a.DateFrom != b.DateTo 
    and b.DateFrom != a.DateTo 
);

或者這个

SELECT DISTINCT a.* FROM Shedulles a
JOIN Shedulles b 
    ON 
    a.ShedulleId != b.ShedulleId 
    and ( a.DateFrom between b.DateFrom and b.DateTo 
    or a.DateTo between b.DateFrom and b.DateTo 
    or b.DateFrom between a.DateFrom and a.DateTo ) 
    and a.DateFrom != b.DateTo 
    and b.DateFrom != a.DateTo