Comment maintenir la cohérence des données avec les déclencheurs MySQL pour les événements d'insertion et de mise à jour ?

MySQL Triggers for On Insert and Update Events

When working with multiple tables, such as the example provided, triggers can be employed to maintain data consistency. In this case, the goal is to update the ext_words_count table based on changes to the ext_words table.

To achieve this, a single trigger can be crafted to handle both insert and update events using conditional statements.

Trigger Code:

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 ;

How the Trigger Works:

• Insert Event: For insert events, the trigger checks if the newly inserted word exists in the ext_words_count table. If not, it inserts the word into the table with a count of 1.
• Update Event: For update events, the trigger updates the word_count field in the ext_words_count table for the updated word. It ensures that the count is incremented by 1.

Notes:

• This single trigger efficiently manages both insert and update operations, eliminating the need for multiple triggers.
• Conditional statements allow the trigger to differentiate between insert and update events and take appropriate actions.
• The trigger's design ensures data integrity by inserting new words and updating word counts correctly.

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