MySQL在插入/更新事件上触发 [英] MySQL trigger On Insert/Update events

问题描述

所以我有两个这样的表...

So I have two tables like this...

ext_words
-------------
| id | word |
-------------
| 1  | this |
-------------
| 2  | that |
-------------
| 3  | this |
-------------

ext_words_count
---------------------
| id | word | count |
---------------------
| 1  | this |   2   |
---------------------
| 2  | that |   1   |
---------------------

我正在尝试创建一个触发器，该触发器将:

I am trying to create a trigger that will:

• 在更新ext_words.word时更新ext_words_count.count.

• update ext_words_count.count when ext_words.word is updated.

进一步复杂化，

• 如果更新ext_words时ext_words_count中不存在ext_words.word，我想将其插入ext_words_count并将count设置为1.

• if ext_words.word does not exist in ext_words_count when ext_words is updated, I would like to insert it into ext_words_count and set count as 1.

我一直在寻找类似的问题:
1. 使用自动增量字段在插入触发之前/之后和
2. 使用触发器更新另一个数据库中的表
试图结合2.这是我到目前为止所拥有的:

I have been looking at similar questions:
1. Before / after insert trigger using auto increment field, and
2. Using Trigger to update table in another database
trying to combine the 2. Here is what I have so far:

DELIMITER $$
CREATE TRIGGER update_count
AFTER UPDATE ON ext_words
FOR EACH ROW
BEGIN

  UPDATE ext_words_count
    SET word_count = word_count + 1
  WHERE word = NEW.word;

END;
$$
DELIMITER ;

任何建议和指导都将不胜感激.或者可能是我忽略的另一种方法，并且一如既往地先谢谢您！

Any advice and direction is greatly appreciated. Or possibly another method that I have overlooked and as always thanks in advance!

更新:
我选择使用2个触发器，一个用于INSERT，一个用于UPDATE，因为我对MySQL中的条件语句不太熟悉.

UPDATE:
I have opted for using 2 triggers, one for INSERT and one for UPDATE because I am not that familiar with conditional statements in MySQL.

DELIMITER $$
CREATE TRIGGER insert_word AFTER INSERT ON ext_words
  FOR EACH ROW
    BEGIN
      INSERT IGNORE INTO ext_words_count (word) VALUES (NEW.word);
    END;
$$
DELIMITER ;

和

DELIMITER $$
CREATE TRIGGER update_word AFTER UPDATE ON ext_words
  FOR EACH ROW
    BEGIN
      UPDATE ext_words_count 
      SET word_count = word_count + 1 
      WHERE word = NEW.word;
    END;
$$
DELIMITER ;

INSERT查询工作得很好，但是UPDATE查询没有更新word_count.

The INSERT query is working great, however the UPDATE query is not updating word_count. Is there something I missed in the update query..?

推荐答案

有了Grijesh的完美帮助和他对使用条件语句的建议，我得以得到 ONE 触发器，它可以完成这两项任务.再次感谢Grijesh

With Grijesh's perfect help and his suggestion to use conditional statements, I was able to get ONE trigger that does both tasks. Thanks again Grijesh

 DELIMITER $$ 
 CREATE TRIGGER update_count AFTER INSERT ON ext_words 
 FOR EACH ROW 
   BEGIN
     IF NOT EXISTS (SELECT 1 FROM ext_words_count WHERE word = NEW.word) THEN
       INSERT INTO ext_words_count (word) VALUES (NEW.word);
   ELSE
       UPDATE ext_words_count SET word_count = word_count + 1 WHERE word = NEW.word;
   END IF;
  END $$    
 DELIMITER;   

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