比较MySQL触发器中的日期 [英] Compare dates in MySQL trigger

问题描述

我有两个表，回合和事件。一轮有很多事件。

I have two tables, round and event. One round has many events.

create table round (
    round_id INTEGER AUTO_INCREMENT NOT NULL,
    round_start_date DATETIME NOT NULL,
    round_end_date DATETIME NOT NULL,
    CONSTRAINT round_pk PRIMARY KEY (round_id)
);

create table event (
    event_id INTEGER AUTO_INCREMENT NOT NULL,
    round_id INTEGER NOT NULL,
    event_date DATETIME NOT NULL,
    CONSTRAINT event_pk PRIMARY KEY (event_id),
    CONSTRAINT round_fk FOREIGN KEY (round_id) REFERENCES round (round_id),
);

当在事件表中插入一行时，我想使用触发器来比较event_date字段新插入的行到圆表中其相应条目中的round_start_date和round_end_date字段中。如果event_date早于round_start_date，则应该使用新的event_date更新round_start_date。如果event_date在round_end_date之后，则round_end_date应该用新的event_date更新。

When a row is inserted into the event table, I want to use a trigger to compare the event_date field of the newly inserted row to the round_start_date and round_end_date fields in its corresponding entry in the round table. If event_date is earlier than round_start_date, round_start_date should be updated with the new event_date. If event_date is after round_end_date, round_end_date should be updated with the new event_date.

这是我的触发器。它不起作用，我也不明白为什么。我在网络上找不到任何其他人试图在触发器中使用datetime类型的地方，所以对于我要去哪里，我没有任何参考。

This is my trigger. It does not work, and I do not understand why. I cannot find anywhere on the web where anyone else has tried to use a datetime type in a trigger, so I have no frame of reference for where I am going wrong.

create trigger update_round_date
after insert on event for each row
begin
    declare curSdate datetime;
    declare curEdate datetime;
    set curSdate = (select round_start_date from round where round_id = NEW.round_id);
    set curEdate = (select round_end_date from round where round_id = NEW.round_id);
    if (NEW.event_date < curSdate) then
        update round set round_start_date = NEW.event_date where round_id = NEW.round_id;
    else if (NEW.event_date > curEdate) then
        update round set round_end_date = NEW.event_date where round_id = NEW.round_id;
    end if;
end;

编辑：我只是无法创建触发器。 phpMyAdmin给我这个错误：
＃1064-您的SQL语法有错误；请查看与您的MySQL服务器版本相对应的手册，以获取正确的语法以在''第4行附近使用

I simply can't create the trigger. phpMyAdmin gives me this error: "#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 4"

编辑2：使用定界符集更新

EDIT 2: Updated with a delimiter set

DELIMITER $$
create trigger update_round_date
after insert on event for each row
begin
    declare curSdate datetime;
    declare curEdate datetime;
    set curSdate = (select round_start_date from round where round_id = NEW.round_id);
    set curEdate = (select round_end_date from round where round_id = NEW.round_id);
    if (NEW.event_date < curSdate) then
        update round set round_start_date = NEW.event_date where round_id = NEW.round_id;
    else if (NEW.event_date > curEdate) then
        update round set round_end_date = NEW.event_date where round_id = NEW.round_id;
    end if;
end$$

这将返回错误：＃1064-您在您的SQL语法；请查看与您的MySQL服务器版本相对应的手册，以找到在第13行附近的''处使用的正确语法

This returns the error: "#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 13"

推荐答案

MySQL可能会在第一个';'处停止，将您的命令解释为：

MySQL is probably stopping at the first ';', interpreting your command as:

create trigger update_round_date 
after insert on event for each row
begin
    declare curSdate datetime;

您必须先将分隔符设置为其他值，然后使用该分隔符终止create trigger命令（并将定界符放回末尾）：

You have to set your delimiter to something else first, then terminate the create trigger command with that delimiter instead (and put the delimiter back at the end):

delimiter ^

create trigger update_round_date 
after insert on event for each row
begin
    ...
end;

^

delimiter ;

我相信结束之后的最后一个分号是必须的。

I believe the last semicolon after end may be necessary.

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