创建触发器时出现MySQL语法错误

在创建以下触发器之后

DELIMITER $$

CREATE TRIGGER NUMERO_OS AFTER INSERT ON custom_values
FOR EACH ROW
BEGIN

IF NEW.custom_field_id = 4 AND NEW.customized_type = 'Issue' THEN

    SET @os = (SELECT MAX(SUBSTRING(value FROM 1 FOR 3)) + 1 FROM custom_values WHERE customized_type = 'Issue' AND custom_field_id = 4 AND SUBSTRING(value FROM 5 FOR 8) = YEAR(CURDATE()));

    IF @os = NULL THEN

        @os = '001';

    END IF;

END IF;

END$$
DELIMITER ;

我在@os='001'；附近发现语法错误

运行MySQL触发器应该怎么做？

尝试重复设置：

如果@os=NULL不是语法错误，而是逻辑错误。如果@os为空，则应为空。不过，这并不能解决您眼前的问题。

IF @os IS NULL THEN
    SET @os = '001';
END IF;