MySQL ON DUPLICATE KEY indsættes i en revisions- eller logtabel

Hvis du vil overveje at bruge en lagret procedure, kan du bruge en DECLARE CONTINUE HANDLER . Her er et eksempel:

CREATE TABLE users (
    username    VARCHAR(30), 
    first_name  VARCHAR(30), 
    last_name   VARCHAR(30),
    PRIMARY KEY (username)
);

CREATE TABLE audit_table (timestamp datetime, description varchar(255));

DELIMITER $$
CREATE PROCEDURE add_user 
       (in_username    VARCHAR(30),
        in_first_name  VARCHAR(30),
        in_last_name   VARCHAR(30))
    MODIFIES SQL DATA
BEGIN
    DECLARE duplicate_key INT DEFAULT 0;
    BEGIN
        DECLARE EXIT HANDLER FOR 1062 SET duplicate_key = 1;

        INSERT INTO users (username, first_name, last_name)
               VALUES (in_username, in_first_name, in_last_name);
    END;

    IF duplicate_key = 1 THEN
        INSERT INTO audit_table VALUES(NOW(), 'Duplicate key ignored');
    END IF;
END$$
DELIMITER ;

Lad os tilføje nogle data og prøve at indsætte en dubletnøgle:

CALL add_user('userA', 'Bob', 'Smith');
CALL add_user('userB', 'Paul', 'Green');
CALL add_user('userA', 'Jack', 'Brown');

Resultat:

SELECT * FROM users;
+----------+------------+-----------+
| username | first_name | last_name |
+----------+------------+-----------+
| userA    | Bob        | Smith     |
| userB    | Paul       | Green     |
+----------+------------+-----------+
2 rows in set (0.00 sec)

SELECT * FROM audit_table;
+---------------------+-----------------------+
| timestamp           | description           |
+---------------------+-----------------------+
| 2010-10-07 20:17:35 | Duplicate key ignored |
+---------------------+-----------------------+
1 row in set (0.00 sec)

Hvis revision er vigtig på databaseniveau, kan du give EXECUTE kun tilladelser, så dine databasebrugere kun kan kalde lagrede procedurer.