mysql自定义sequence

CREATE TABLE sequence_table (
    sequence_name VARCHAR(50) NOT NULL,
    current_value INT NOT NULL DEFAULT 0,
    increment INT NOT NULL DEFAULT 1,
    PRIMARY KEY (sequence_name)
);

INSERT INTO sequence_table (sequence_name, current_value, increment) VALUES ('my_sequence', 1, 1);

DELIMITER $$
CREATE TRIGGER before_insert_my_table
BEFORE INSERT ON my_table
FOR EACH ROW
BEGIN
    DECLARE next_value INT;
    UPDATE sequence_table SET current_value = current_value + increment WHERE sequence_name = 'my_sequence';
    SET next_value = (SELECT current_value FROM sequence_table WHERE sequence_name = 'my_sequence');
    SET NEW.id = next_value;
END$$
DELIMITER ;

CREATE TABLE my_table (
    id INT PRIMARY KEY,
    name VARCHAR(50)
);

INSERT INTO my_table (name) VALUES ('Alice');
INSERT INTO my_table (name) VALUES ('Bob');

START TRANSACTION;
SELECT current_value INTO @next_value FROM sequence_table WHERE sequence_name = 'my_sequence' FOR UPDATE;
UPDATE sequence_table SET current_value = current_value + increment WHERE sequence_name = 'my_sequence';
SET NEW.id = @next_value;
COMMIT;