Bagaimana cara memeriksa apakah suatu variabel NULL, lalu mengaturnya dengan prosedur tersimpan MySQL?

@last_run_time adalah 9.4. Variabel Buatan Pengguna dan last_run_time datetime satu 13.6.4.1. Sintaks DECLARE Variabel Lokal , adalah variabel yang berbeda.

Coba:SELECT last_run_time;

PERBARUI

Contoh:

/* CODE FOR DEMONSTRATION PURPOSES */
DELIMITER $$

CREATE PROCEDURE `sp_test`()
BEGIN
    DECLARE current_procedure_name CHAR(60) DEFAULT 'accounts_general';
    DECLARE last_run_time DATETIME DEFAULT NULL;
    DECLARE current_run_time DATETIME DEFAULT NOW();

    -- Define the last run time
    SET last_run_time := (SELECT MAX(runtime) FROM dynamo.runtimes WHERE procedure_name = current_procedure_name);

    -- if there is no last run time found then use yesterday as starting point
    IF(last_run_time IS NULL) THEN
        SET last_run_time := DATE_SUB(NOW(), INTERVAL 1 DAY);
    END IF;

    SELECT last_run_time;

    -- Insert variables in table2
    INSERT INTO table2 (col0, col1, col2) VALUES (current_procedure_name, last_run_time, current_run_time);
END$$

DELIMITER ;